I created this Window Jam / Stop to keep my windows from opening and shutting violently when strong winds pass by our building. This is for large windows that open vertically. I put this thing into the opening in the window and it provides the support needed to keep the window open and prevents it from slamming shut. I used it most of the winter time and during the summer without an issue. I am not sure what the tolerance is as I have no way to test that but it has worked great for me and the rest of our office.Open the window and slide the stop / jam down the side of the window. Make sure you are holding the window open the whole time. I made the handle long enough so that your fingers shouldn't be at risk but for safety reasons you would always have one hand on the handle of the window to prevent it from slamming shut on you. Once the jam / stop is in the window it should prevent the window from slamming shut again. To remove the jam, lightly tug on the window handle and slide the jam / stop out. It's pretty simple and I have included pictures in case i am not being clear.