This project was built and designed by Rob from Let’s Make Things. It’s a clever clamping jig designed to simplify glue-ups on picture frames, especially when working with tight mitered corners.
Built from plywood and common shop hardware, this adjustable jig uses sliding blocks to secure each frame corner with only two clamps. It’s an efficient, budget-friendly alternative to specialized clamping tools and a great addition to any woodworking setup.
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The Frustration of Clamping Mitered Corners
Miter joints are often challenging to glue and clamp without shifting or gaps. Traditional jigs with notched boards work, but they can be finicky and require new pieces each time the frame size changes.
Rob wanted a flexible, reusable solution that would eliminate the hassle of remaking jigs for every frame. His design makes it easier to achieve tight, square joints using only two clamps and materials most woodworkers already have on hand.
A Jig That Adapts to Any Frame Size
The core of the jig is a set of plywood baseboards with integrated grooves. These grooves allow sliding blocks to adjust for different frame sizes without needing to rebuild or resize the jig.
Static blocks are fixed at each end, while movable blocks slide along the tracks. The frame pieces fit snugly between these sets of blocks, and once clamps are applied, the corners are squeezed tight for a strong, accurate joint.
Building the Track System
Instead of using commercial T-tracks, Rob creates his own track system from plywood. Strips are glued and fastened to the base to form channels just wide enough to fit the sliding blocks.
The groove system allows each block to glide smoothly while remaining firmly in place. To ensure free movement, the bolt heads inside the blocks are recessed below the surface using shallow counterbores.
Creating the Sliding and Static Blocks
The sliding blocks are carefully sized to move easily inside the plywood grooves. Each block has a bolt running through it, which can be tightened to lock the block in place once the desired position is found.
Rob also includes static back blocks at each end of the jig. These act as fixed stops, keeping the frame pieces aligned during the glue-up and helping maintain squareness.
Hardware and Fastening
Simple hardware like bolts, washers, and wing nuts is used throughout the build. Each block is secured with enough strength to hold the pressure from the clamps during the glue-up process.
The blocks are either glued and nailed in place or fastened with screws, depending on whether they need to remain stationary or adjustable. The result is a stable, repeatable jig system that holds tight without shifting under pressure.
Assembly Tips and Optional Finishing
To keep the jig operating smoothly, Rob recommends applying paste wax or a coat of polyurethane to the sliding surfaces. This reduces friction and helps the blocks glide more easily.
For glue-up protection, painters tape can be added to the surface to prevent glue squeeze-out from sticking to the jig. This helps extend the life of the jig and keeps it clean for repeated use.
Using the Jig for Frame Assembly
Once the jig is set for the desired frame size, the shorter frame pieces are placed between the blocks on each end. The longer frame pieces are added to complete the rectangle.
Two clamps are applied—one at each end—to pull the miters together. The pressure from the sliding and static blocks holds everything tight, allowing for accurate alignment and a clean glue-up.
Because the jig adjusts quickly to different dimensions, it can be reused for a variety of frame sizes without extra setup. It’s especially useful for small or medium-sized frames where standard clamps may not reach or apply even pressure.
Why This Jig Works So Well
This design addresses several common issues in mitered picture frame assembly:
- Only two clamps are needed, reducing clutter and setup time.
- Blocks adjust easily for different sizes, so no new jigs are needed.
- The jig holds corners tight and square, leading to better results.
- All materials are affordable and often already available in the shop.
The sliding track concept also makes it easy to fine-tune positioning, which is helpful when adjusting for slight size variations or correcting fit.
A Practical Jig Worth Adding to Your Shop
For woodworkers who regularly make frames or small mitered projects, this jig is a simple way to boost efficiency and consistency. It’s an approachable build that requires only basic tools and common materials.
Rob’s video walks through each step of the process in clear detail, making it easy to replicate or customize the jig to your own shop needs. It’s a helpful tool that can save time, reduce frustration, and lead to better-looking miter joints.
Get Rob’s plans here: https://makethingswithrob.com/picture-frame-clamping-aid/.