I believe they hold the bottom of the I beam frame members to keep them from rolling either in or out. Basically hold the frame rails square.
I had a hitch made for mine. Using 2" square tubing made a "H" and where the cross bar on the "H" is, is where the 2" tube goes that extends to the rear. Welded 4"x3" angle to the ends of the "H" and then BOLTED it to the bottom of the frame rails with grade 5 bolts. 2 bolts in each angle piece. 8 grade 5 1/2" bolts thru the bottom frame I beam flanges hold it on. "H" frame is about 30" front to back and extends to the frame rails. The hitch shop said bolting is stronger than welding and makes the hitch easy to remove if need be.
Have towed a small trailer (1,800lbs) about 6K miles with the hitch, not a single issue. Inspected it a couple weeks ago and no issues seen.
About $500 out the door. Let me know if you need hitch pics.
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2012 Ram Laramie 3500 DRW 4x4 3.73 Tow Max Pkg B&W Companion 60 gal RDS aux fuel tank. 2014 Montana 3150RL, 2 A/C's, Leather, 6 Point Jacks, Splendede WD2100XC, Mor/ryde X-Factor, Duravis 250 tires with TST 507RV monitors. 2 x Honda EU2000's
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