From Dorchester DIY
- Although the weights were eventually very useful, we did have to take off the sharp corners on four sides to get them to slide smoothly inside the sash box, because the top and bottom edges kept catching on the inner side of the sash box where the access panel fitted in. So I wouldn't recommend these weights to people who don't have a way to smooth down the sharp edges where required, especially if they were going to use them for the lower window (which has the access panel). Taking these edges down with a grinder didn't seem to make a significant difference to the weight balance with the window and we got a very good result in the end.
If Ironmongery Direct wanted to improve the design of these weights they could smooth down all the sharp corners.