One-Timers in maps

[Cheetohs]

I was curious as to why somethings only happen in a certain location on the map, and not on all similar brushes in it. For some examples:

On the bridge, or crossroads, at allied spawn, the building to your left that has the 2 archways... on the 2nd one if you jump at a side angle at the arch, you will carry up the arch to the top.

Or... Why (before the mods) in the Sewers can you jump through the archway and get underthe map, and not do it everywhere?!

Why, in The Hunt, in the rubble pile, if you jump at a certain corner of the wall, will it carry u up the wall, why doesnt it do this at EVERY corner?

If you follow what im asking, or dont know, just ask.... but ive looked at the .maps and in these locations and couldnt find any reason WHY it allows you to do these 'glitches.'