Thomas & Betts 141 Conduit Locknut Brand: Thomas & Betts. Part Number: 141. T&B Conduit Locknut, Case Hardened, 1/2 in, For Use With: Rigid/IMC Conduits, Steel, 1-7/64 in H x 5/32 in THK. Additional Description: TB -141 1/2 INCH CASE HARDENED STEEL LOCKNUT. Catalog Description: 1/2 Inch Steel Locknut for Use With Rigid/IMC Conduit..