Instructions
Look at your Tom Thumb bit and distinguish the top from the bottom. The rings attached to the cheek pieces at the sides are much closer to the mouthpiece at the top.
Place the Tom Thumb bit on a flat surface in front of you. The rings for the headstall are at the top and the rings for the reins are at the bottom. The top ring should have a second, smaller hole. This is to keep the cheek piece from twisting.
Orient the cheek piece so that the larger rings on the top are facing in toward each other and the smaller ones are turned out.
Identify the cheek straps. These are the pieces that attach to the bit. They should have buckles on the outside so that you can buckle your Tom Thumb bit into place.
Open the buckles on the cheek straps on the headstall. Insert the straps into the larger top rings on the Tom Thumb bit.
Fasten the buckles on the cheek straps so that the smaller rings are enclosed within the strap.
Try the headstall on your horse and ensure that you have chosen the right length at which to buckle the cheek straps. The straps should be flat against your horse's face, but not pulling.
Clip your reins into the bottom rings on the Tom Thumb bit.
How to Connect a Headstall to a Tom Thumb Snaffle Bit
Tom Thumb bits are Western bits named after the small locomotive on the Baltimore and Ohio Railroad that lost the famous locomotive-versus-horse race in 1830. This little locomotive was famous for having the most powerful engine of its size. Likewise, the Tom Thumb bit is a powerful training device, severe enough to break a horse's jaw when it's used with a heavy hand. If you are absolutely certain that you want to use a Tom Thumb bit on your horse, you need to make sure that you have attached it to your headstall correctly.