What's the trick behind...

Placing a sentry on a block in Lazy town? (or any other block)

I now how to get on the block, bu no matter how I turn or point my sentry it won't "pop-up"

Plz tell me what I'm doing wrong.

You're playing lazytown

*Sigh*

Or any other cement block outside of LazyTown.

*Adds Gman_Nick on his to dominate list*

Good luck.

Have you seen sentry's there before?

Offcourse, it's something a lot of engineers do there, somehow I've not been succesfull in placing one.

Quote:
If you've ever had to download a new version of the map, it could have been patched...

On complicated surfaces (like the blocks, which have a dent in the middle, I believe) then you can only usually build an object if you're facing "downhill". If any of the object is facing "uphill", the build template won't usually appear.

How do you get a sentry on the tall platform on Goldrush....there's no obvious way to get up there ....also how do you jump on your  dispenser

The answer to both of your questions is "crouch-jump onto your dispenser".

To get on the raised platform on PL_Goldrush (part 1), you have to build a dispenser right on the corner of the platform behind it; then crouch-jump on your dispenser (make sure you have 125 metal first) and start a teleporter exit building on the platform while you're jumping past it...with practice it's possible to just jump on the platform from the dispenser. (I've done it, but it's very hard)