using these to hold 2x3 across my cargo trailer to create a raised bed (storage under) for stealth convertible camper. Didn't want to ONLY use my 6x15 enclosed cargo trailer for caping. I use it to haul sound gear for gigs. When I put these beam holders in to the E-Track, they wobble a bit, so, make sure to cut your wood EXACTLY to length... Start long & trim back as needed... the more firm a fit, the better they work... This is the first time I've used any E-Track product & I was surprised to find that I couldn't screw these to the wood beams & just click them in... you have to leave the wood just sitting there... the beam holder can only be removed by pulling back the spring loaded holder clip on the top & angling them up at about 30 degrees.. then kinda pulling down & out of the top retainer.... so, for convertible like I'm doing... cut to a good length & don't fasten to the holder to the beam. I also purchased the D-ring for E-Track.. that way, I can haul gear & use ratchet straps to the same E-Track socket. I got the individual sockets instead of the 5 foot sections... that way it's cheaper & I can simply put them where I want them.