This is the larger of two styles of leathercraft 'stitching horse' tools.
You can use it to hold your leather craft project so that you have both hands free to concentrate your stitching or lacing.
The upright section has leather-lined jaws to hold onto your work without damage, and the flat base tucks under your leg when you sit down, so the stitching pony is held securely with your work in front of you at just the right height.
This item comes in two pieces which simply screw together and the third wooden component is a 'turn key' which you can use to open the jaws of the tool, though you may not need to use this as the jaws of the stitching horse are easily adjusted to apply a light pressure to your work, using the sprung wing nut assembly on the upright of the tool.
Full assembly and usage instructions are included with this stitching horse.