it was like a short youngman board,with a right angle steel on one end and a extending flat plate on the other,
the idea being you measured out to the back of the shaft wall from the door lip,put say 4 inches on it,stand the platform in the doorway and lower it till it hit the back wall obviously trapped at say 5 degrees up onto the angle iron which then was bolted through the top into the floor,
had its own handrails that sat in,,strange but i saw belgian thyss fitters doing one on a hotel in liverpool,they said all they needed scaffold for was gated handrails on the floor openings and access with ladder to the pit,
got on it 9 floors up and it settled about an inch,you could smell eggs at the 1st floor opening!