"I did not buy my first Record clamp heads from Screwfix but inherited them from my father. I needed more and got two sets as a present. One uses 25mm x 40mm-ish timber for the bar and can use any length of timber available. This makes the clamp heads much cheaper than a Record sash clamp and it will do the same job. With my fathers clamp set he strengthened the timber with Dexian Angle bar and was able to apply pressure greater than many bench vices. This tool is overlooked by many DIYers and I can't think why. We repaired 5-bar gates using these clamp heads so that shows how universally useful they are. Will buy more if I need more than four to do a big job."