A pace stick is a long stick usually carried by warrant officer and non-commissioned officer drill instructors in the British and Commonwealth armed forces as an aid to military drill.
A pace stick usually consists of two pieces of wood, hinged at the top, and tapering towards the bottom, very similar to large wooden drafting compasses used on school blackboards. They are usually shod and fitted with highly polished brass. They can open so that the tips separate at fixed distances, corresponding to various lengths of marching pace, such as "double march", "quick march", "step short", etc. When opened to the correct pace length, the pace stick can be held alongside the holder's body by the hinge, with one leg of the stick vertical to the ground, and the other leg pointing forward. By twirling the stick while marching, the stick can be made to "walk" alongside its holder at the proper pace.
Otherwise, while on parade or when marching, it is normally carried tucked tightly under the left arm and parallel to the ground, with the left hand grasping the stick near the top.