I just received my rail mount in the mail and I'm a little perplexed as to the hardware to use. Is there a reason that both ends of where the nut and bolt head will be are recessed using the hex pattern? I imagine that when I purchase hardware for this, either the nut or the bolt head will fit perfectly into the recess, but if both ends are recessed, that will prevent the user from continuing to tighten down the bolt to ensure a tight fit on the rail. Any help would be appreciated. I am considering buying a washer that will keep the bolt head from falling into the recess, but I'm not sure if that would be as structurally sound.