This inexpensive and jig (that can often be made with off-cuts of wood) is the handiest jig you might have in your shop for aligning all sorts of woodworking projects and keeping them square, which of course makes them that much easier to work with.
Wood projects that are out of square and hard to work with, and for the woodworker, often disappointing to continue to work with or sell and there are only 2 things that contribute to out-of-square projects ....
... and those 2 things are:
1 - wood cuts that are not straight or even or they are un-matched (sides are unmatched in length)
2 - not taking the time to align the pieces after it has been cut
For now, we will assume you have cut the wood evenly and that sides even, such as the opposing sides of the picture frame, both sides (left and right) are exactly the same lengh and both top and bottom sides are also exactly the same length. Now all you need to do is put them together so that all the corners align with NO gaps!!
A squaring jig could be the most important jig you ever make, they are quick, handy, easy to make and will last for years and years unless you decide to make a bigger one with more accessories, which is actually a good thing, because then you are using it and getting superior results.
My latest version was made from and off-cut of 3/4" MDF for the base and the sides are laminated Beech which was also off cuts from a previous project. I did purchase new T-Nuts and a couple of bolts for this project. The purpose of the MDF is that it is flat and remains flat it's entire life and the laminated Beech will also remain flat and straight it's entire life without bending of warping ... that's the advantage of laminated wood ... very stable.
I did add some accessories because from time to time I need to clamp wood to the frame to aid in the assembly. There are all sorts of different clamps you could use for this, I just chose these because I had them on hand and they work fine.
I use 1/4" T-Nuts because the are sufficiently strong and easy to find bolts that fit them.
As a quick side note, I talked about the fact that I round of the outside corners of my Carpenter's Squares because sometimes I find they do not fit properly into some corners. More in home-reno than woodworking, but either way, I never miss the very sharp edge of these squares and find them invaluable to be able to fit them into corners they would not otherwise be able to fit into, so that I can then make better measurements and adjustments.
Here is the link to the video on "Squares" I made a few years ago --- https://bit.ly/3Ok10ic
Below are close ups of the laminated sides of the frame along with the rounded over tops of the bolts that I selected especially for this project because they will not interfere with any of the clamping or working surfaces. Also notice that the sides of the frame do NOT connect, the reason for this is so that if any dust of chips get into the corner, I can easily slide it out that crack and leave myself with a nice crisp, accurate 90 degree corner.
As you say in the video, I was the sides and the base so that if any squeeze-out glue comes from a project, it is easy to clean up and does not affect the jig or the project in any way.
I have been using my previous versions of this squaring jig for over 20 years. They are quick to use and always accurate and what I like most is the weight of them, helps to hold the projects in place and I don't have to stop to set up some sort of a temporary jig or attachments to my carpenter's square to do the same thing. The jig is handy in my workshop and always ready to go.
Taylor Tools Affiliate Store - https://lddy.no/18zkg
Article Link - https://bit.ly/3o5TLA0