I wouldn't use these to mount stuff that is going to take a beating, but for things that are weaker than the bolts themselves, these are amazing for mounting accessories not made for track mount:

all COARSE thread

1/4-Inch Zinc Coupling Nut - I had to order these. They are double female.

1/4 inch carriage bolts - various lengths come in handy. I started running empty ones along my track so I can just put things on them.

1/4 inch nuts

1/4 inch wing nuts

Don't forget washers!

Some of this stuff is reasonably priced at Atwood's. Lowe's and Home Depot were awful for stuff like this around where I live.