Those lower bolts also attach to the hunk of machined steel shown in the first picture. It is also attached in the rear to one of the cross members shown being constructed earlier.  The gear leg will come up through the hole and be clamped to this piece with two bolts. The leg will continue up and also be connected to the spar at the top.

The second picture shows the sections almost completely riveted together. The job is finished in the last two pictures.