PartDesign Pocket

Introduction
'Create a pocket with the selected sketch' - This tool takes a selected sketch as its input, and produces with it a 'pocket'. A pocket is essentially an extrusion of a sketch that subtracts from the geometry it protrude into. For example, if a sketch were made simply of one circle on one face of a cube, then the pocket formed by that sketch would manifest as a hole 'drilled' into the cube: