This is the Idler Pulley Plate. It can be used with both V-Slot and OpenRail.
The idea behind this plate is to give you a mountable yet movable plate for your Smooth Idler Pulley. This works great as it allows you to easily tension your belt.
There are a lot of possible mounting configurations for this plate.
This design was inspired by Barton Dring of Buildlog.net
Black Anodized Finish
3mm~ (1/8″) Thick
Belt Driven linear actuator examples: