WHILE COMPLETING A 200 HOUR SERVICE ON A 637 SCRAPER, EMPLOYEE WAS STEPPING OFF THE FRONT ENGINE USING THE STEPS MOUNTED TO THE MACHINE. HE LOST HIS FOOTING WHILE DISMOUNTING AND STUMBLED BACKWARDS FALLING INTO THE TOOLBOX DOOR OF HIS SERVICE TRUCK. HE CAME INTO CONTACT WITH THE DOOR IN HIS BUTTOCK AREA, CUTTING HIS BUTTOCK WHICH REQUIRED STITCHES.