Editing Combination square (section)

=== Heads ===
The heads, occasionally called anvils, are attached to the rule by sliding the rule into a slot in the side of the head. The head is then tightened in place via a lock bolt or lock nut which engages with a channel running the full length of the rule, allowing the head to be tightened on at any point along the rule.<ref name=":1" /><ref name=":3" />

The standard or square head has three adjacent flat faces, two of them meet square to one another, and the third face is angled away at 45°. When attached one face is parallel to the rule, one face is perpendicular, and one face is at 45°. The standard head usually incorporates a small spirit level and a small removable [[scriber]].<ref name=":1" />

The protractor head has a flat reference edge which is attached to an adjustable 180° [[protractor]] or (sometimes called a turret) with a graduated scale in both directions for reading both the angle or the complement angle.<ref name=":4" /> The protractor head sometimes includes a small spirit level.<ref name=":1" /><ref name=":3" />

The centre finder head has two faces meeting at 90°, when attached one edge of the rule [[Bisection|bisects]] the two faces at 45°.

The heads are manufactured from either forged steel, cast iron, die-cast aluminium, die-cast zinc, or plastic. Aluminium and zinc heads are cheaper than steel and iron, but less durable and more prone to inaccuracy.<ref>{{Cite magazine|last=Rae|first=Andy|date=March 2015|title=The Multitalented Combination Square: A whole lot of tool in one small package|url=https://www.woodcraft.com/blog_entries/the-multitalented-combination-square-a-whole-lot-of-tool-in-one-small-package|magazine=Woodcraft Magazine|pages=50–54|issn=1553-2461}}</ref> Cast iron and steel heads are also notably heavier. The heads are usually painted except for the flat machined reference faces.{{Citation needed|date=October 2020}}