Looking for this part on a Phillips window. It is a vertical sliding window.

There are four of these on the bottom half of the window. Two on the left side and two on the right side, one towards the top and one towards the bottom. I think they sort of resemble a screw on face guide, but not quite, this one has a different shape and little projections on it. I really need to find out what it is, I need to replace them on all my windows because without them they are wobbly, I'm afraid they'll break and hurt my children! Please help! Thank you!