The mounts bolt to the frame using threaded inserts, most of which already existed.  The mounts are triangulated and have angled supports.  The vertical seam in the rocker panels that extends down about an inch is notched to pass the supports through.

I built the main rails first, then held them up in place with a jack, some blocks and stands, and then cut the leg tubes to fit.  I also trimmed back the bottom of the front wheel well and re-formed the plastic liner with a propane torch to give more wheel clearance.

The finished rails look pretty spiffy and have worked well.  The legs were originally going to have 4 bolts through them, but I ended up only using 2.  I never got around the drilling the additional holes.  The rails were also going to sit tight against the rocker panels with a layer of 1/8" rubber in between to give them extra support and distribute weight along the entire rocker panel.

This caused a lot of vibration though in the body, especially in the foot well area.  What I did for a while was remove the rubber mat so there was a gap between the body and the nerf.  Then I put the mat back in and drilled and threaded holes into the nerf bars for bolts to go through the seam in the rocker panel.  

These bolts don't really support weight, but they did seem to tie the nerf and body together better and the vibration became much less of a problem.  It still was noticeable at first, but after a week of driving it wasn't any more.

The space in the bar allows for a hi-lift jaw to hook into and they will easily support the weight of the vehicle when used as a jack point.

The first improvement was that I used more spacers closer together in the gap between the main and outer rails.  I have noticed on my nerfs the outer rails bends a little more than I like when on the hi-lift.  Especially on the end where it has the least support.  The additional supports here seemed to be perfect and there was barely any deflection at all on the hi-lift.

Second was that I made the gap a little wider.  1.5" instead of 1".  I've found on my nerfs that I can stand on them fine, but I'm using my toes.  These Rodeo nerfs extend out a little further and allow the balls of my feet to rest on the bars so they're easier to stand on.

The biggest improvement though is the mounts.  I didn't want to weld them on, but I wanted something better than my mounts too.  I ended up welding brackets on that the nerfs bolt to.

The brackets are cut from 1/4" steel and welded to the top and bottom of the frame rails.  The mounts have two vertical tubes instead of a flat plate and the tubes slide in between the mounting tabs.  They're bolted together with 1/2", grade 8 bolts.

This really turned out to be a *very* solid mount.  These bars do not touch the body at all, and there is very little noticeable deflection in them when on the hi-lift.  They're spaced down about 1/2" from the rocker panels.

The tabs are horizontal like this rather than vertical for a reason.  The front leg (which I don't have a picture of) is angled to match the angle of the frame rails at the front of the truck.  With the mounting tabs vertical, there would be no way to get the nerfs on and off.  With the tabs horizontal like this, the nerfs will slide straight in and out, even with the front mount being angled. 

Some day (probably when I do my bumpers), I'll re-build my nerfs using these improvements.  I may do the mounts a little different yet again.  Maybe some type of clamshell type mount that wraps around and pinches down on the frame rail rather than welding mounting tabs to it.