Our airline's runway analysis has a landing distance for landing beyond threshold and another one for landing beyond glide slope. For each distance it has the corresponding maximum weight allowable for that distance/runway.

My question is, what regulation or Ops Spec or other guidance addresses which landing distance you should use?

My assumption is that if you're on a visual approach, perhaps the beyond threshold distance is usable. If an ILS approach is used, perhaps the beyond glide slope distance is requied. However, we all know that one cannot descend below glide slope until necessary for landing. Is the beyond threshold distance ever permitted?

Any opinions or references to where this might be covered would be great.

Thanks!