The second movie specifically, The Two Towers, has shown that you cannot stick the ring up your arse and keep it in the correct orientation for this to happen.
I’d think wearing the ring up your ass should make you invisible, the ring has to count that as “wearing it”; but alas, it doesn’t make invisible people wearing it as a pendant, so it really prefers finger penetration.
The second movie specifically, The Two Towers, has shown that you cannot stick the ring up your arse and keep it in the correct orientation for this to happen.
I’d think wearing the ring up your ass should make you invisible, the ring has to count that as “wearing it”; but alas, it doesn’t make invisible people wearing it as a pendant, so it really prefers finger penetration.