Thomas & Betts 142-TB Conduit Locknut Brand: Thomas & Betts. Part Number: 142-TB. T&B Conduit Locknut, Case Hardened, 3/4 in, For Use With: Rigid/IMC Conduits, Steel, 1-3/8 in H x 3/16 in THK. Additional Description: TB -142-TB 3/4 INCH CASE HARDENED LOCKNUT. Catalog Description: 3/4 Inch Steel Locknut for Use With Rigid/IMC Conduit..