If the mechanic then flips over the same end of the wrench 180 degrees, the angle of the wrench will be slightly different allowing the open end of the wrench to slip onto the fastener and continue motion of the wrench. Each time the wrench handle contacts interference in a limited space, flipping the open end of the wrench over will allow for continued fastener movement without having to remove the wrench to use a different angled wrench or other type of tool. The box end or closed end of a combo wrench has many styles as well but there are two main types with referal to the number of teeth or flat edges inside the boxed or ring end of the wrench. The most common type of box wrench is the 12 point box end. the reson for 12 points inside the boxed end of the wrench is to allow the mechanic to apply the wrench to a six-sided bolt or nut in more angles than would be allowd by only a six-point wrench. with a 12 point end of a box wrench, the tool only needs to lift off the fastener and rotate 30 degrees before it can slip down on the fastener again. With a 6 point box end wrench, the wrench handle will have to be lifted off and rotated 60 degrees to be able to slip back in place on any six-sided fastener. The added degrees of sweep make a 6-point box wrench less desirable for use in confined spaces. However, use of a 12-point wrench on corroded or slightly stripped nuts or bolts may cause the six sides of the fastener to strip. One great advantage of the 6-point box end wrench is it's uniform contact surface to all six-sided fasteners.