thanks for your feedback and suggestions. Yes, that is a lock tumbler on the yakima rack. I didn't have time to put in the actual lock yet but I'll for sure get it put in. Adding a jam nut didn't even cross my mind at all, and I'm glad you pointed that out as a security measure. I'll pick up these nuts from home depot and apply them onto the threaded bolts for more added security. this forum is the best to get the answers you need and also get suggestions! thanks again!
2011 335i with M-Sport Performance package, Carbon Fiber interior trim, gloss black kidney grills