Achieving repeatable linear motion is the first and biggest challenge of building a reprap from scrap. These mounts let you you try many sizes of printed bushings with ease until a suitable match is found. It has 2 screw holes to attach to a wood frame, and a groove for a bushing to sit in with a small hole for a ziptie retainer. The ziptie will tighten up on any movement that is not on the axis of desired motion so this ends up being a very solid mount. I'm using these bushings: https://www.thingiverse.com/thing:13631