This is what it sounds like - you can climb a series of trapdoors as though they were ladders. Trap doors are more expensive to craft than ladders, in terms of resources, so if you want to build a bunch of trapdoors and climb them, now you can. 

If you simply want one trapdoor in the middle of a ladder, don't bother with this mod; you can climb that space without this addition. 

Co-Authored with Aramil

Original Author - ZigTheHedge - Necessaries

Continuing Author - Stahl - StillNecessaries