This is a simple bowstring separator, which can be used for changing your peep sight, installing silencers or servings, or whatever else you could want to do with it. Simply insert it between the strings where your peep is, and enjoy not needing a massive bow press anymore!
Depending on your printer and method of printing, there may be small, practically unnoticeable surface defects (e.g. sharp extrusions, dangerous edges, etc), which may cause damage to your bowstring. Be sure to check for and sand down these little buggers before you insert the separator into your string.