Are you sqare?
Here are some squares and their names for them.
1) speed square. This is probably one of the the most common squares you will see on the worksite. It's small and very versitile.
2) Framing square. This is a large square used where accuracy is important. They are usually 18 X 24 inches
3) Combination square. This square moves and has a 45 degree angle built in. Very handy and they come in several sizes and configurations.
4) Layout square. Usually used in sheet metal. Sometimes you can find these in fine tools. They last for generations.
5) Sliding T bevel. This is a very handy tool that enables you to set an angle and copy it to your material. NO tool box is complete without one of these. You may not use it often but when you need it you got it.
6) T square. This particular one is indispensable in doing Sheetrock. It is usually 48 X 24 inches
Always check the level on your combination square before purchase. They are notoriously out of level. And check your squares after dropping on a hard surface. May need to file down a high spot at the corners where it has hit a hard surface.
Very constructive post.