Protractors

Two decisions cover this category. Scale first: a 180 degree semicircular protractor is the classroom standard because school geometry measures from a straight baseline and the half disc keeps the drawing visible, while 360 degree circular protractors are for bearings and navigation work. Then the material — clear plastic for general schoolwork, and a stiffer or metal edge where it doubles as a straightedge. Often bought with compasses or as part of a geometry kit.