A common boot failure is when the three pin holes under the front of the boot become so damaged they cannot engage with the ski binding satisfactorily, often from misaligning the three holes in the sole of the boot to a three-pin binding. If hired boots are to be used with a three-pin binding system, always check the state of the holes on the boot, to ensure they are in good condition.
If the three holes on the sole of the boot are torn out, dry the front section of the boot thoroughly, using gentle heat from your stove. Apply cloth tape over the three damaged holes, the sides and front of the boot. Add as many layers as is practical, especially at the front of the boot to create as much strength as possible. The limiting factor is the width of the binding. Only apply as much tape as the binding will allow, so you can still slip the boot into the binding. Gently heat cloth tape as this assists its adhesion to the boot. Spike the holes for the three pins.
Its surprising how this simple repair, if done with care, can get you back to your car and still manage to do a few telemark turns along the way. This is a temporary repair, and your boot is ready for the rubbish bin.