about 3 years ago - SylenThunder - Direct link
This was long reported as a bug, and during a16 Joel finally said "it's intentional", right along with the hatch elevator.
Then a17 dropped, and it was "fixed an exploit with the hatches and haybales".
about 3 years ago - Red Eagle LXIX - Direct link
Originally posted by Vagrant: I see that Frame blocks cannot be picked up too.

I used to build hay bale staircases when I explored some POIs. When I was finished with the place, I picked up the hay bales back.

Also, I used to keep a "disposable" staircase in my bunker house. In case of a zombie breach on the 1st floor, I evacuated on the 2nd floor and picked up the staircase frame blocks.

I guess it's time to go smoke crack and go ♥♥♥♥ myself.
Yes they can, and with the use of the shapes menu you have portable ladders, portable any shape.
You want the 'Frame Shape' (particle board looking stuff) for picking up. Not any material named shape.

Originally posted by Vagrant: Well my bad, cobblestone frames cannot be picked up and assumed wooden frames followed the same rule.

I guess it's a matter of time before it gets nerfed too.
You never used to be able to pick up the flagstone or cobblestone before so that isn't changed.