How can you rape someone?

It seems like it'd be pretty hard to get an erection while trying to hold someone down that is kicking and punching and screaming

someone posted a website ages ago about some old loon who had invented this....badger like trap to shove up your minge and if someone stuck their cock in you then BAM! Bye bye mr winkie.

Apparently they used to do something something similar in vietnam using razor blades?