Help Identifying Item On Trailer

[Triton]

I have a 803 on a PU-798a trailer and I am trying to identify what this is in the picture and what is it used for. I searched the very long TM on the trailer but it was not mentioned. I've had this unit almost a year and haven't noticed it that square box, on the back side it is not connected to anything.

 

[Zed254]

Jack Spacer. http://www.appliedcompanies.net/images/documents/TM9_2330_392_14_P.pdf . Check page 105/342. Allows use of HMMWV Jack for trailer tire change. Here is the jack for the unarmored HMMWV: https://colemans.com/shop/military-vehicles/u-s-g-i-scissor-jack/ . The Jack Spacer fits onto the stud of the jack. The curved part of the Jack Spacer fits against the trailer's shock absorber mount.

 

[Triton]

Ok I got it now, I didn't have that TM but it has a lot of good info!
Thanks