I have a large outdoor porch swing with a heavy duty metal frame. It needs to have the canvas seat replaced. If I buy the vinyl material used in boat seat upholstery how would I attach it around the metal frame?
If you think you may want to change out the fabric periodically, you could also try heavy duty, outside appropriate Velcro...you would have to use gorilla glue or a wood friendly glue to stick the one side of the Velcro to the wood bottom (least it looks like wood...if I am wrong, then you would need to find a glue that works on the material you are dealing with). Then just match up (and stitch or glue down) the other side Velcro to its mate and you are good to go.
I like using Velcro because it is easier to remove if I have to for cleaning, etc.
I would use a heavy duty staple gun.