In the early 70's I worked around Leeds erecting Street lighting. The Poles would already be in position, so we would just slip the lighting unit onto the pole and tighten it up. We didn't have hydraulic lifts like today. I seem to remember it worked on cog wheels. On the back of the lorry, there was the small working cradle, sitting inside a bigger cradle, which sat inside a bigger one, which also sat inside a bigger one. And they would go up one at a time till it was fully extended. Does anybody know what they were called?