Roof rigger mobile suspended user crane. Never!
They have one for parapets too:
More: MIO Roof Rigger Overview
Harnesses save workers after crane collapse - GIF
Mobile crane collapses while installing billboard, with possible dozer assist - GIF
1934 Aluminum Reduction Works coke pile gantry crane - photo
Offloading four 300-foot cranes from a ship onto a pier - video and photo
Roadside car-scrapping crane - GIF