Anything that doesn't move :-) There are only so many trellises one can include in an average-sized garden without it looking ridiculous, so I use anything else that is the slightest bit permanent - fences, trees and shrubs, a large stump, a big hunk of driftwood, obelisks and pillars, various curled and contorted ironworks I have either made or acquired, even simply trained up the columns at the side of my porch. And of course there are those clematis that are more herbaceous in nature and don't require support - these I just allow to ramble on the ground or creep through other plants.

All that plus I had DH add a lattice panel to the top of the fence and trained them up bird netting stapled on to 1 x 1's to lead them up.

He also made free standing trellises with 2 x 4s and lattice panels.