What is this frame bolt for?

[Elwood]

The ol' memory not being what it used to be, and too much time elapsed since I disassembled this part of my truck, I can't recall what, if anything, the bolt circled in red below is for? It's on the right frame rail, aft of the front running board bracket and just forward of the front transfer case crossmember. With the external tooth lock washer, it looks like it should be for something electrical like a chassis ground, but it's tucked in on the right frame rail inboard of the muffler. The small bolt above it is for a bracket on the inside of the frame rail that holds the wiring harness.

I took photos from when I did the disassembly (see below), so I know what it looks like, but I can't figure out what it's for.

Any ideas?

[w30bob]

Elwood,

The bottom bolt that you have circled is where the ground cable from the battery box attaches to the frame. The upper bolt holds 2 wiring brackets to the inside of the frame.

regards,
bob

[just me]

Yeap. That is were my ground cable is. Mine also has a braided ground lead to the body from there.

[Elwood]

Thanks guys. The ground strap had disappeared from my truck by the time I got it, but the bolt was still there.