The Purlin Clamp is perfect for installing to purlins, I-beams and bar joists up to 1" thick. 3/8" × 2.5" square head set screw for locking onto I-beam. 3/8" × 1" grade 5 Hex Head Bolt supplied to connect load or use for 3/8" – 13 tpi threaded rod. Micro-grooves for secure connection to beam. 1" thick.