Stuck: BG collision with maps drawn with DATA

So, recently I have started using the "DATA" Map Engine. But, I have something that keeps me doubtful. The BG Collision. So, I also want a collision with a ladder, you can enter it, and then you can use it while pressing up or down. Please help. I'll appreciate it! _{*I have got it on a Thread and I will use this engine :P}

look at other people's implementations of collision if you want some good ideas as in, downloading their games and seeing how they made it

I can do that maybe... But the search engine from here sucks. Just shows me a few things that it found. _{But yeah I will use your technique...}