Miter Gauge

A miter gauge rides in the slot (or slots) machined into a table saw's top, sliding the workpiece through the blade at a set angle -- 90 degrees for a standard crosscut, or any other angle for a miter cut, set and locked via a protractor scale on the gauge's head. It's the correct guide for any cut across the grain or at an angle; using the rip fence instead for a crosscut is a well-known kickback risk, since the offcut can get trapped between the fence and blade with nothing to stop it from binding.

Stock factory miter gauges are notoriously imprecise at their protractor scale's fine graduations, which is why many woodworkers add an auxiliary fence with stop blocks, or upgrade to an aftermarket gauge, for cuts where the exact angle actually needs to be trusted rather than eyeballed close.