Combination wrench sets come with a box end design on one side of the handle and an open end design on the other side. These combination sets provide multiple head sizes so they can be used with a range of fasteners. The box end is an enclosed head end that fits around and grips the entire head of the fastener. It provides more contact to the fastener than an open end design and can apply more torque since the box end is less likely to slip off the fastener compared to the open end. The open end design allows access to the fastener from the top and side compared to the box end that can only access a fastener from the top.