To clarify - knee pads can help reduce the onset of issues such as bursitis. The issue I wasreferring to is a bit different: hooked blades should be used in a fixed blade heavy duty Stanley knife, being pulled towards the user (it can take a fair bit ofveffort). The hooked blade tips are known to break and they can also pull out of the material (or the knife in the case of poorer knives) - at which point you can end up stabbing yourself in or above the knees. I've seen vinyl fitters who have quite a collection of small, old scars from just such accidents, which are not unknown