What is this on a crane?

[aclivity]

Has caused many a chat amongst the people I work with - what is the yellow thing that is attached to the crane?

It's been on and off the crane over the last couple of weeks or so?

[TheEnd]

It looks like it is there so get stuff sideways into a building.

[chrisj_abz]

im guessing its a beam to allow the load to be swung under an obstruction/overhang which would normally foul the crane wire??