Definitions for "Combination Square"
Combination squares are typically used for general carpentry work. They are effective for fast and accurate measuring or marking of 90 degree, 45 degree and 180 degree angles, as well as for checking depth.
link A square that measures both 90 degree and 45 degree angles.
Big brother to the smaller try square, the combination square features a sliding handle that often includes a built-in level. It's useful for squaring and marking boards and lumber for crosscuts, and it also doubles as a depth gauge and miter square. Many also include a metal scribe. Home Improvement Encyclopedia