CATHEADS, for Well- Drilling / Servicing Machinery: PSO-D&P, §6642 Chain Used for Spinning Lines PSO-D&P, §6645: Lines Used on Catheads: PSO-D&P, §6644: CATWALKS: GISO, §3273(d) Boom Block, Access to: GISO, §4926: Drilling Wells, Access to: PSO-D&P, §6572: Overhead Clearance: GISO, §3273(d) Over Water: CSO, §1603(b) Size Requirements ...