The photo shows a combination square and level from the time of Pharaoh Ramses (about 2,000 years B.C.). I could not get to the exhibit, so I bought a glossy photo book, and this page was in the book. The level is a plumb line with a mark on the crossmember of the square. I always wanted to build one of these.
Step 1: Rip three pieces
Wood always moves with changes in humidity. Egypt is a very dry climate, so precision instruments from wood might work there. I made my Egyptian square and level from 1/2 inch plywood because it will not shift with changes in humidity.
I ripped three pieces 2 1/4 inches wide. I made the legs of my square 20 inches long each. The original in the museum exhibit has legs about 14 1/2 inches long.