With a bit of leather/cloth wrapped around the blade, they're perfectly capable of cutting through softish metals and hard plastics. The tension is mostly optio

With a bit of leather/cloth wrapped around the blade, they're perfectly capable of cutting through softish metals and hard plastics. The tension is mostly optional, since the teeth usually only point towards the pull, resulting in the blade providing usable tension. Source: Not a car thief, but have misplaced my hacksaw, for small tasks, far too many times.