Rein chains are used with romal reins, NOT with split reins. They serve several purposes:
a. chains help to balance the romal reins adding weight and feel (as do the buttons) to the reins,
b. chains aid in keeping the romal reins drier when a horse drinks,
c. chains protect the romal reins themselves when a horse (or other critter) chews,
d. chains should break before the romal reins do in an emergency especially if used with rein connectors.*
*Our CC rein connectors (Aaron developed the finished edge button style originally) are inexpensive. They attach the rein chain to the romal reins (not the bit end). They don't tend to hang up or interrupt the communication signal. In an emergency, the connectors should break early sparing your romal reins.
Commercial romal reins often come with braided connectors which are very strong and can cause increased damage in a wreck. They can twist and deaden signals to the horse.
The rein chains attach to the bit stirrups, stirrups with clevises (swivels threaded through the bottom of the stirrups---columpios) or the rings (ganchos). Do it yourself, or find a guy with a vice or two pairs of heavy pliers. Open the S hooks at the end of the rein chains and then closes them on the bit rings, through the stirrups or the clevises.
Scissor clips and any other type of snaps came about in the arena for fast changing of reins and other gear between horses, bits or riders. Some also use the clips if their horses have a lot of movement in their strides. They tend to cut down on the swing and sway of the chains and/or reins.
We don't like this practice because they:
1. don't allow for rein chains which help with balance and sway and serve to protect the romal reins,
2. often twist and also deaden the signal sent through the reins so feel of the signal can be impaired,
3. tend to gum up, rust or other "horrors" over time,
4. in an emergency, they can hang up more than clevises on your bit and, if using a slobber bar, they may hold more than ganchos,
5. they are not traditional.