Thomas & Betts 143 Conduit Locknut Brand: Thomas & Betts. Part Number: 143. T&B Conduit Locknut, 1 in, For Use With: Rigid/IMC Conduits, Steel, 1-11/16 in H x 13/64 in THK. Additional Description: TB -143 1 INCH STEEL LOCKNUT. Catalog Description: 1 Inch Steel Locknut for Use With Rigid/IMC Conduit..