No drilling through the crossbars. The hex head bolt along with a washer (I had to trim the washers to fit - making them more oval shaped) fit into the t-channel. I kept the rubber gasket in place. It’s a tight fit, but it works. Bolt length will be subjective to your application but 2” long...
I need to correct my op. Now that I remember correctly, The Yakima t-bolts were what I used to mount the Pelican Vault Box not the awning. Awning hardware was a little more difficult. I bought 3/8-16x2 bolts, angle ground off half the head height, added a washer that also needed to be trimmed to...