Put a bolt in the threaded end of the axle. Pull to expose the snap ring groove.
Leaving the ring off won't hurt anything. Back at the Jeep dealer, maybe half of the Jeeps were missing those snap rings.
1) '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS, hubcaps. 2) '82 J20 360/T18/NP208/3.73, KOs, 7600 GVWR 3) '75 CJ-6, 304/T15, PS, BFG KM2s, soft top 4) '95 VW Golf Sport 2000cc 2D