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.
Watch the full video and subscribe to Rob’s channel:
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/.
Matt’s Take
These are my personal thoughts and tips based on my own experience in the shop. This section is not written, reviewed, or endorsed by the original creator of this project.
Picture frame glue-ups can be one of the most frustrating parts of woodworking — you’ve got four mitered corners that all need to come together perfectly, and traditional clamps often work against you by pushing the joints out of alignment. Rob’s sliding block approach is really smart because it applies pressure from multiple directions at once, keeping everything locked in place while the glue sets.
The beauty of this jig is in its simplicity. Rather than buying expensive specialized clamps that might only work for certain frame sizes, you’re building something adaptable from shop scraps. That plywood track system is particularly clever — it gives you the precision of commercial T-track without the cost. When you’re making the grooves, take your time with the fit. You want the blocks to slide smoothly but not have any slop that could affect your joint alignment.
One thing I really appreciate about this design is how it addresses the common problem of frames going out of square during clamping. Those static blocks at the ends act like reference points, helping maintain your 90-degree angles throughout the process. If you’re new to frame making, this jig will save you from a lot of the trial-and-error that comes with getting miters to close up tight and stay put.