When it comes to assembling a woodworking project, it's easy to reach for a box of woodscrews. They're convenient, reliable, and work well for all kinds of shop projects and furniture. But screws aren't always the most attractive or practical way to connect two pieces of wood.
Sometimes you want to reinforce a miter joint without visible fasteners, align boards during a panel glueup, or build a strong frame without cutting traditional mortise-and-tenon joints. That's where wood fasteners come in.
Splines, dowels, biscuits, and Domino loose tenons offer four practical alternatives. Each uses a piece of wood to connect adjoining workpieces, but they differ in how they're installed, the tools they require, and the types of joints they're suited for. Here are four wood joinery methods I use in my shop, along with some tips for getting the most out of each one.
Why Use Wood Fasteners Instead of Screws?
Wood fasteners offer several advantages over conventional metal fasteners. They can be completely concealed within a joint, eliminating the need to hide screwheads with plugs or filler. They also provide additional gluing surfaces and can help align parts during assembly.
In some applications, wood fasteners can even replace more involved traditional joinery. For example, a pair of dowels can serve a similar purpose to a small mortise-and-tenon joint when connecting frame members. A spline can reinforce a miter joint while adding an attractive decorative detail.
That doesn't mean wood fasteners are automatically stronger than screws or traditional joinery. Their performance depends on the joint design, grain direction, dimensions, and how the assembly will be loaded. The advantage is having more options available when choosing how to build a project.
1. Spline Joinery: Reinforce Miters and Align Panels
Splines are one of the simplest wood fasteners you can make in your shop. A spline is a thin strip of wood that fits into matching grooves cut into two adjoining workpieces. Once glued in place, it connects the pieces and provides additional gluing surface.
I often use splines when adding solid-wood edging to plywood panels or reinforcing miter joints. They're also useful for keeping adjoining boards aligned during assembly.
One advantage of spline joinery is that you don't need specialized equipment. For a 1/8"-thick spline, a flat-top table saw blade can cut the matching grooves. The spline itself can be made from a hardwood blank.
Choosing the Right Grain Direction for Splines
Grain direction is an important consideration when making splines. For many edge and miter joints, a cross-grain spline provides better resistance to the forces trying to separate the joint.
A long-grain spline may split along its grain when the joint is stressed. Orienting the grain across the joint can help resist this type of failure. However, grain direction should also account for seasonal wood movement, especially when joining wide solid-wood panels.
How to Make Wood Splines on the Table Saw
Making your own splines is straightforward, and a single hardwood blank can produce several matching pieces. Start by selecting a blank that's large enough to handle safely and orienting it so the finished splines have the grain direction needed for the joint.
The method shown above uses two table saw cuts for each spline. First, make a cut with the blank on edge to establish the spline's width and form a narrow tab. Then place the blank flat on the table and make a second cut to separate the spline.
Arrange the setup so the narrow cutoff falls freely away from the blade rather than becoming trapped between the blade and rip fence. Use appropriate push blocks and workpiece support. Once the splines are cut, test their fit in the grooves. They should slide into place without excessive force, leaving enough clearance for glue.
Woodsmith Tip: If you're making several identical joints, cut all the matching grooves with the same setup before sizing the splines. This makes it easier to achieve a consistent fit throughout the project.
2. Dowel Joinery: Strong, Simple Connections with a Drill Press
Dowels are another versatile option for joining wood. They're essentially small, round loose tenons that fit into matching holes drilled in adjoining workpieces.
One reason I like dowel joinery is that the mortise is simply a drilled hole. There's no need to square the ends or fine-tune a rectangular opening. With accurate layout and drilling, you can create a strong joint using basic shop tools.
Dowels work well for joining frame members, assembling cabinets, and reinforcing other woodworking joints. They can also serve as an alternative to screws in certain applications, particularly when you want to avoid visible metal fasteners.
How to Make a Dowel Joint
The key to accurate dowel joinery is making sure the holes in both workpieces line up. For a frame joint, I typically use two dowels to connect the end of one member to the edge of another. Here's the six-step process I use to lay out, drill, and assemble a dowel joint.
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| Layout. Begin by marking the locations of the dowels across the jointline on the faces of both workpieces. | Centerline. Score the centerline of the first workpiece on the edge. I add a pencil mark for visibility as well. | Transfer Layout. Use a square to transfer the layout lines from the face to the edge. |
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| Drilling. Head to the drill press to make the dowel holes. Use the fence to keep the holes even. | Chamfer. Finish the dowel holes with a slight chamfer. This will make tapping the mating pieces together easier. | Dowel Centers. Use dowel centers to transfer the locations, then drill and chamfer the mating workpiece. |
Step 1: Lay Out the Dowels. Begin by marking the dowel locations across the joint line on the faces of both workpieces. Use consistent reference faces so the parts will align during assembly.
Step 2: Mark the Centerline. Score the centerline along the edge of the first workpiece. I like to add a pencil mark as well to make the line easier to see.
Step 3: Transfer the Layout. Use a square to transfer the dowel locations from the face of the workpiece to its edge. The intersections of these marks establish the drilling locations.
Step 4: Drill the Dowel Holes. Head to the drill press and use a fence to keep the holes aligned. Set the depth stop so the holes provide adequate depth for the dowels, with a little clearance for excess glue.
Step 5: Chamfer the Holes. Use a countersink bit to create a slight chamfer at the opening of each hole. This helps guide the dowels into place during assembly.
Step 6: Transfer the Hole Locations. Insert dowel centers into the first set of holes and bring the mating workpiece into position. Press the parts together to transfer the locations, then drill and chamfer the corresponding holes.
Once the holes are complete, dry-fit the joint to check the alignment. When everything fits properly, apply glue, insert the dowels, and bring the pieces together.
Using Dowels to Reinforce Existing Joints
Dowels aren't limited to joining two pieces edge-to-edge or end-to-edge. They can also be used as pegs to reinforce other types of woodworking joints.
For example, a dowel can secure a rabbeted case assembly without leaving a visible screwhead. Dowels can also be installed through a mortise-and-tenon joint to provide additional mechanical reinforcement. This type of pegged joinery is useful for furniture and workbenches, where the joint may be subjected to repeated stress.
The size and placement of the dowels matter, however. Make sure there's enough surrounding wood to prevent splitting, and consider how the joint will be loaded before substituting dowels for screws or other fasteners.
3. Biscuit Joinery: Quick Alignment for Panels and Casework
A biscuit is a small, oval-shaped piece of compressed wood that fits into matching slots cut into adjoining workpieces. When glue is applied, the biscuit absorbs moisture and swells slightly, helping create a snug connection.
Biscuit joiners were once common in woodworking shops, and although other joinery systems have become popular, I still find them useful for certain tasks. Their biggest advantage is speed. A biscuit joiner can cut matching slots quickly, making it convenient for aligning boards during panel glueups, assembling casework, or joining mitered parts.
How a Biscuit Joiner Works
A biscuit joiner is essentially a small plunge-cutting tool equipped with a circular blade and an adjustable fence. The blade cuts a crescent-shaped slot into the workpiece, sized to accept a matching biscuit.
To make a joint, start by marking the biscuit locations on the adjoining pieces. Set the joiner's fence height and cutting depth, then adjust the fence angle if necessary. Align the tool with the layout marks and plunge the blade into each workpiece to create the slots.
Once all the slots are cut, apply glue, insert the biscuits, and assemble the joint. The elongated slots provide some adjustment along the length of the joint, making biscuits useful for aligning workpieces during glueup.
When Should You Use Biscuit Joints?
I find biscuits especially handy for aligning boards during panel glueups. They can help keep the faces flush while you're applying clamps, reducing the amount of flattening and sanding needed afterward.
They're also useful for certain miter joints and cabinet assemblies where alignment is important. However, biscuits aren't a direct replacement for every traditional joint. Their relatively shallow engagement and thin profile limit their usefulness in heavily loaded frame joints.
For applications where the joint needs to resist significant bending or racking forces, a properly sized mortise-and-tenon or loose-tenon joint is generally a more suitable choice.
4. Domino Loose-Tenon Joinery: Fast, Accurate Furniture Joints
The final wood fastener is the Domino loose tenon. Although it may look similar to a biscuit, a Domino is thicker and fits into a deeper, rectangular mortise with rounded ends.
This makes it useful for a different range of woodworking applications, including furniture frames, cabinet assemblies, and other joints that would traditionally use mortise-and-tenon joinery.
The Domino system uses a specialized joiner to cut matching mortises in the adjoining workpieces. Prefabricated loose tenons are then glued into the openings to connect the parts.
How a Domino Joiner Works
At first glance, a Domino joiner looks and operates much like a biscuit joiner. However, instead of using a circular blade to cut a shallow slot, it uses an oscillating mortising bit to create a deeper opening.
To make a joint, mark the mortise locations on both workpieces. Set the fence height, cutting depth, and mortise width, then plunge the cutter into each piece. Once the mortises are complete, apply glue, insert the loose tenons, and assemble the joint.
Because the tenons extend farther into the adjoining pieces than biscuits, they provide a substantial gluing surface and can be used for structural frame connections.
When Should You Use Domino Joinery?
Domino loose tenons are useful when you need the strength and alignment of a traditional mortise-and-tenon joint but want a faster, more repeatable process. They're particularly convenient for projects involving multiple identical joints, such as tables, chairs, cabinet doors, and furniture frames.
The primary drawback is the investment in the specialized joiner and its cutters. But for woodworkers who frequently make mortise-and-tenon joints, the time savings can be substantial.
You don't necessarily need a Domino joiner to take advantage of loose-tenon joinery, either. A plunge router and a shop-made mortising jig can be used to cut matching mortises for loose tenons.
Which Wood Joinery Method Should You Use?
Each of these wood fasteners has its place in the workshop. The choice depends on the type of joint you're making, the strength required, and the tools you have available.
For simple miter reinforcement or panel edging, a spline may be all you need. Dowels are a practical option for frame construction and other joints where you want to avoid visible screws. Biscuits make quick work of alignment during glueups, while Domino loose tenons offer a convenient approach to more demanding furniture joinery.
The important thing is to understand what each fastener does well and choose the one that fits the project. Adding these four techniques to your woodworking skill set gives you more ways to build strong, accurate assemblies without relying on screws for every connection.
Explore More Woodworking Joinery Techniques
Wood fasteners are just one part of the joinery options available in your workshop. If you're interested in learning more about traditional mortise-and-tenon joints, spline joinery, or cutting accurate mortises with a router, Woodsmith has several techniques and shop-made jigs to help you get started.
RELATED ARTICLES: How to Use Biscuit Joints for Perfect Panel Alignment
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Whether you're building a simple shop project or a piece of fine furniture, understanding these different joinery methods will help you choose the right connection for the job.
