These are replacement parts for kitchen cabinets made years ago by a company called Merillat, which is, I believe, acquired by Masco. Part of the drawer slide is this part, called a "mono adapter". The sides of the part tend to wear out over the course of years of use. It turns out that you can order replacements for these if you email someone at mascocabinetry.com. It's $10 for a pack of 4, plus shipping. However, I'd already made a model and printed some out. The replacements I printed worked great.Printed the "right way up" as shown in the image of the part. I added support structure. Printed in ABS with 2 side borders and 3 layers top/bottom solid. Also 30% infill. I used support material because of the "slot" on the bottom and mechanically removed the support material later. You could modify the model and just remove the slot... I think that might work too.