The Crescent 4" NITE EYE™ Trim Square, part CTS04. It has an aluminium body. Supplier specification: SQUARE 4" TRIM ALUMINUM NITE EYE.
A square is only as good as its reference edge. Check it against a known straight edge before trusting it, and keep it from being dropped — a square that has been knocked out of true reads confidently and wrongly, which is worse than an obviously damaged tool.
