I need to cut the legs of my chair a bit because it is too high for me. It would not have been a problem but all legs need to be of the same length so I am looking for straight accurate cuts at the same distance from the end. I was trying to find out how to do it without much luck. Any ideas?
Woodworker's solution: put chair on flat surface. Put shims under feet as needed to level and stabilize it. Using a pencil on top of a suitable scrap of wood, mark all sides of all four legs at the same height above the table. Cut to these lines. If necessary, fine-tune with sandpaper, but generally this will be close enough that flexibility in the materials will do the rest.
One idea that comes to mind is to get an appropriately sized length and width of aluminum bar, cut it to the size you need, and clamp it into the fence screw in a circular saw with an appropriate blade. Angle the circular saw so that it makes a level cut (a torpedo level would be useful), and place the end of the aluminum bar against the seat bottom.
Supposing that you have a level chair now, the first thing to do is measure the front legs (from the seat bottom to the tip); multipy the length by 3/4 (or whatever fraction you desire). Make your mark (3/4 length from seat bottom). Then measure the back two legs and multiply the their length by 3/4 (use the same pre-chosen fraction as used for the front legs). Again make your mark. Double check your work by setting the chair up-right and measuring from the floor straight up (vertically); to the marks on the legs. You're not measuring 1/4 the length of the leg, but instead the height of the marks from the floor. They should all be the same. The legs will be even if you cut them accurately.
Edit- another possible answer is to use a level to mark the legs. Make all of the marks level.