that when the bolt 13 is abutted against either end of the aperture 12 the tooth 7 will then be properly aligned with the corresponding outer slot 17 as illustrated in fig3 to overcome the force of the spring 15 the operator of the backhoe using the hydraulic controls not shown of the backhoe bears down with the tooth 7 against the ground or wall of the trench and then shifts the frame rearwardly relative to the tooth 7 compressing the spring 15 when the spring 15 has been compressed sufficiently to free the lug 7a from the slot 17 the operator actuates the controls to swing the boom so that the tooth will pivot on the spindle 8 and relocate in front of the slot 17 corresponding to the desired new tooth position the controls are then operated to free the tooth so that the lug 7a will pop into the new slot 17 due to the force of the spring 15 thus the position of the tooth can be changed without the operator leaving the controls of the backhoe in fig4 another embodiment of the invention is illustrated in this embodiment the frame 19 is in the shape of a bucket a tapered blade or tooth 20 is pivotally mounted on the frame 19 by pin 21 the tooth 20 can move relative to the pin 21 in a slot 22 in the tooth.