One thing to note with measuring tapes is that you’ll notice the end of
the tape has a hook on the end for holding onto things. The hook will
move back and forth slightly. This is to compensate for the thickness of
the hook. If the measuring tape didn’t have this feature you would get a
measurement slightly off when you hooked the tape to the edge of a
board or pushed it against the inside of a drawer.
Speed Square
The speed square can be used to do many things, but the two things it’s
usedformorethananythingelseistomakesureacornerissquareor90q
(degrees), and to mark lines that are square to an edge by hooking the
flanged side of the square to the edge of a board and drawing a line.
There are 360° in a circle and 180° in a straight line. If we intersect that line with
another line that’s perpendicular, where they meet cuts the 180° in half or 90°.
Another way to say that a corner is 90° is to say its “square”.