I entered archery classes a while ago. As part of the 'class materials' the instructors lend us bows, arrows and protection gear
Now, I'm not sure of since when these classes have been going, but that protective gear has quite likely seen more hands and arms than what they were meant to endure (and are still in use)
And then, there is also the occasion when there are more students than equipment (and things tend to get far messier then)
Of course people is allowed to bring personal equipment; and if it's personal you don't have to share it
Second problem here was, well, there is only one armory (that I know of) that sells archery equipment; it's in no way an easy place to go to (for a mere student with few time and without car) and it tends to be overpriced....
So, well, why not make my own equipment?
Pen / pencil
Galvanized Wire (or similar)
Cold silicone glue (I recommend, but you can try with another kind) or thread and needle (if you have and can sew leather)
Shoelace (optional) or other
Step 1: Step 1 - make the patterns
There are many, many styles out there, look up the one you like the best, or the one you considered the best, or the easiest one you can find, or the one you considered safest. It's your guard, so you decide.
Do take into consideration this, though; the part you really want to protect is the one nearest to your elbow joint (or rather the opposite side of the elbow joint) not the wrist joint, because the bowstring doesn't hit there.
Now, with paper and pen, and your arm, make a draft of your guard.
Cut it and check if the size works for you
The good thing of paper? You can check and modify if you want