Inpenetrable??
Neither a ram's legs nor his penis are bigger than the gaps in sheep fencing regardless of how tightly strung.
It didn't look comfortable (head flung back and front legs on the the fence) and could have been downright dangerous but he got his quick jump in and was away in moments. The ewe was also looking very pleased with herself.
This was sheep netting, don't know what brand strung tightly between wooden posts.
Neither shoulders nor head were through the fence, and I dare say unless the ewe had been the slapper she was 99.999999999999% of the time he wouldn't have managed anything but this time he did and I was there to witness it, mores the pity. He was a young ram though so probably bendier than most.