Picture Frame Exact 90 deg. Corner Jig

Got the original idea from David Picciuto's web site " Make something ", and then tweaked it for myself.  I questioned the exact 90 degrees until I studied it more, but it will end up pretty much as it says.  Made out of laminate shelving 1" thick, 15x36 inches in size. This was sized to fit my table saw but sizes are what you want to make. Made my own runners out of Hickory to fit. Bought a new square (aluminum) and made sure it was exactly 90 deg. and screwed it to the base. Adjusted everything with my digital measuring tools to as close to 45 deg as possible on the point of the square. Cut the slot through the square with a carbide blade. The square is raised slightly to allow a space under its edge for the sliding stop block. This works on the principle of using the inside of your precut rabbit groove on your frame material, no extra math involved. The way this works is that you can be off the 45 deg. slightly and it won't matter. For example, 44 deg. when cut on the frame piece is 44 and turned for the next cut on the other end will be 46 which still equals 90. Mine was 44.8 degrees when other end was cut it was 45.2 degrees perfect 90. All left cuts will be one size and all right cuts will be the other and will naturally match up when assembled. I made a lot of practice cuts on various scraps, and it worked like a charm. Go to David's site to get more info on how it works or for the build. The stop block has a clamp to hold it exactly where it is put. I just finished my first frame with it and the corners were perfect 90s. Will put it in projects later.