This is called a face guide. I'm afraid that we don't have this exact guide, but you might be able to use our 67-002 screw on guide as a replacement. Look it over and see what you think.
The Face Guides essentially stabilize the sash by help keeping it in place, which I am assuming is the friction you're describing. Basically they're meant to prevent any wobble or sudden movement. I hope that makes sense. Let me know if you have further questions.
By the way, I did a little further digging. This looks a little like our 67-030 Face Guide also; this might be a better match function-wise. Take a look and see what you think!
