This is a 12" wide auxiliary support that helps prop up the out-feed from long boards as you run them through your machine tools. It’s like having an extra pair of hands at the other end and is an exceptionally good value. The solid primary roller works for skinny stock, like trim and molding, and a set of omni-ball rollers support wider boards and planks. Sturdy, adjustable bipod legs, allow you to match the height of your table saw, etc. to a maximum of 42". Adjusts with a steel thumb knob. Great for DIYers who don’t have the room to build a permanent extension structure around their table saw.