Ladders

Hi all, i have imported my model buildings which have ladders built in and around them
What would be the best way to make them work with climb function?

I see some plugins and some youtube with coding but a bit lost in which way to go

Well i worked out ladders
Got my building with image of ladder, put my ladder model i just made in position and works fine.
I worked out i can Attach the two so i can move them around the map in sync with each other.

how do i make it as one (to reuse without adding ladders again) and keep ladder working, if i Merge them it looses the collision box and function i just made?