Trailer Parts › 4 Way Male Harness Image 1 of 1 4 Way Male Harness from $8.26 The 4way male harness is used for small utility trailers. Power, Ground, brakes and lights. Size: 20' 25' 30' 35' Quantity: Purchase Added! The 4way male harness is used for small utility trailers. Power, Ground, brakes and lights.