Can I replace only the J-hook on an old interlocking threshold?

Often, yes. If the existing interlocking threshold is still in good condition but the door-bottom hook is missing, damaged, or badly bent, the J-hook can often be replaced without replacing the entire threshold.

The important part is compatibility: the replacement hook must line up with and engage the existing threshold profile. Check the old metal and door preparation before ordering.

See the replacement bronze J-hook strip. The installation guide shows how the hook is recessed and fitted to the door bottom.