crane help - where am I going wrong?

Using the inbuilt crane object, I can never get it to do anything. Ive tried hooking it up all sorts of different ways, yet it doesn't extend anything at all. I thought it was bugged as a beta object, but I've seen othsrs use it successfully, so clearly I'm doing something wrong.

Any pointers greatly appreciated!

*update: PeterZ pointed out that it only works in ADVENTURE MODE, so that's where I was going wrong! Thanks!*