I have 2 old metal swing sets. One is a bean trellis in the garden. The other is in the chicken run, supports a truss roof system for the flock's winter sunroom.
I extend the length of trellis in the garden by poking a piece of 10' electrical conduit into the hole at the top of the A on one end. The conduit then stays parallel to the ground, at same height as top of the A. The other end of the conduit passes through (2) 2 x 4's which are drilled at the top for the conduit to pass through. The bottom ends are buried in the soil. This gives me about 18' of trellis, and could easily be extended from other end as well.
I extend the length of trellis in the garden by poking a piece of 10' electrical conduit into the hole at the top of the A on one end. The conduit then stays parallel to the ground, at same height as top of the A. The other end of the conduit passes through (2) 2 x 4's which are drilled at the top for the conduit to pass through. The bottom ends are buried in the soil. This gives me about 18' of trellis, and could easily be extended from other end as well.