In an earth working apparatus (10, 12), a separate router bit (32) and support (34) are removably secured along a generally vertically extending side member (22) of an earth-working blade (18). By forming them of separate elements, the router bit can be made of inexpensive plate metal while the support can be economically forged since it is in relatively protected position between the router bit and side member. The support is reversible and has a first lip (36) overlying the upper end (38) of the router bit and a second lip (40) underlying the lower end (30) of the side member whereby forces are transmitted directly from the router bit to the side member through the support instead of through the removable bolts (50).