Well, as I'm new here I guess I can still ask stupid questions. What are frame stiffeners? How do they work? Bolt on weld on? Is there an after market source? What threads are there here? (didn't have much luck with a search)
Hope to get something soon, gettin' the "itch" bad again....

 

Frame stiffeners is plating that goes on the XJ unibody rails to make it stronger and therefore take more abuse. Most of the ones I see are welded on, and it is probably best that way. I might be wrong but I think Detours off-road sells a bolt on stiffener that is supposed to go with their rocker guards.

EDIT: Here is a link to Detours, it is currently unavailable. http://detoursusa.com/xjrokslyders.php

 

Detours bolts on in 2 places but then needs to be plug welded to the unibody frame

EDIT: Nevermind he does offer just a bolt on version

 

i have these there pretty bada** http://www.jcroffroad.com/Merchant2/...ry_Code=XJMISC if u want to see some pic's of them on my jeep look in my photos

 

I have TnT stiffeners...noticable difference in body stiffness and less moaning and groaning of the body when off road...definitly worth the price of admission in my book... my install pics are in my album also
Cameron