I just sent an inquiry about an unknown window corner. On the site, an inquiry that I previously sent concerning a wheel (87-094) showed up which lead me to the corner (18-073) that uses that wheel. I have ordered 8 of them.
In the process of ordering, I saw that there is a video on the page of 18-073 for the "top sash guide 18-033" not a bit like 18-073. The video is obviously in the wrong place. In ordering the 18-073 the description was "top sash guide", obviously wrong since 18-073 is a window frame corner.The 18-073 page should reference the wheel 87-094 I hope that this helps you identify the errors and correct them.
Bill