I posted a working ladder I created for my own game a long time back after TGC removed them.
It may stil be around and might be one of those some of you have found recently.
Anyway I have attached it again. It is a segment and all the files needed including the instructions are included in the attached .zip file.
It is not perfect by any means but at least it provides a ladder which functions.
Dont complain if it is not perfect. I do not support it. Use it or dont use it as you wish. I may update it at some time and in the meantime its free for anyone to take and modify it if they can make it better for the benefit for the whole community. It is a WIP for anyone that wants to develop it further and I am sure there are some that may be able to do so. At the moment it suits my purposes and although some find it difficult to climb I have no problem with it personally. If its a challenge in a level then all well and good as far as I see it. I dont like to make levels to easy for the player especially when under attack.
You can stack the ladder with enough effort if I remember correctly but because it has a slight angle the higher the stack the further from the base of a wall the bottom might be so it does not look so good. With a single height of course the angle is hardly noticable in gameplay.
Ideally there is no substitute for a Ladder which TGC can incorporate so the engine recongises the object correctly but dont hold your beath for that to be reintroduced. I have no idea why its such a problem for TGC but apparently there is a either some technical reason or simply not the will to reintroduce ladders to FPSC.