Update: 23.09.16 added V2- made it a bit tougher. My V1 broke after serval month in usage
V1: support for CTC 3D Z-Axis Brass Nut to prevent screwheads from destroying wood plate Fully designed and public in http://OnShape.com. Search for "CTC 3D Parts". You can copy and modify the project according to your needs. E.g. adjust to your screw head size.