or for as long as you need it to hang! These plate clamps will definitely grip any mild steel that you place inside them, as long as you don't exceed their weight capacity. Remember that use on hardened steels is not recommended, because the serrations on the jaw faces are not able to get a proper "bite" on the surface of the material, and could slip off unexpectedly. However, if you use these clamps as intended, you will be very satisfied in their performance for a long time.