try to saw away at your shackles

You pass the time waiting quietly, with little to do, in almost complete silence. The palace settles in for the night.

You reach around on the ground, looking for some way to break free. You find it, eventually, a piece of sharp metal. You begin to grind away at your shackles. The sound of metal against metal echoes in the silent chamber.

Suddenly, you hear a noise down the hall. It sounds like footsteps. Should you continue sawing or wait until the footsteps pass?