Make a groove in the bottom of the door leaf. The lower guide roller will move along it, which does not allow to deviate to the sides of the lower part of the cape when opening and closing. It is convenient to do this with a woodworking machine or milling cutter. But if you do not have one, then this can be done with a chisel and hammer. It is advisable to first mark the end of the door leaf with a pencil, draw a line where the groove will take place. In this case, it must be remembered that the groove should be even, do not have a zabin and burrs. If you make a groove with a chisel, at the end it is desirable to fade it.