Square head bolts manufactured to GB/T 8-1988, GB/T 35 and DIN 478 feature a square-shaped head that fits a matching square recess. Once seated, the head resists rotation during nut tightening, so the head does not normally require a separate holding tool.

Material options are carbon steel grades 4.8 and 8.8, with A2 (304) and A4 (316) stainless steel available. Surface finishes include black oxide, blue-white zinc, yellow zinc and hot-dip galvanizing. Common applications listed are steel brackets, guardrails, agricultural machinery, solar supports, tunnel supports and construction machinery. Confirm required size, thread and standard when ordering.