Used with a sewing machine, it holds the venting cap in place while sewing into the fabric.
Simply cut a hole in the fabric large enough to place the boat vent cap snugly in. Then position the pole cap on top of the raised center of the installation tool to keep it in place while sewing into the fabric.
Use this sewing fixture in the construction of mooring pole covers, boat covers, and enclosures to prevent mold and mildew. Tool #45771 is a fundamental accessory for marine fabricators.