Assembling a ger, the middle stage.

Once the walls are up, the roof comes next. The roof ring (technically: toono) is lashed to the two vertical poles that support it, and then held up in the center. People then place the roof poles (un') in holes in the ring and they are then hooked into the wall.

The exact number of roof poles various based on the size of the ger, but from what I can tell, about 70 would be a rough ballpark figure. Some of the same size will use more or less poles.