The Purlin Clamp is perfect for installing to purlins, I-beams and bar joists up to 1" thick. 1/2″ × 2.5″ square head set screw for locking onto I-beam. 1/2″ × 1″ grade 5 Hex Head Bolt supplied to connect load or use for1/2" – 13 tpi threaded rod. Micro-grooves for secure connection to beam. 1" thick.