Back in the day, we had one of the great sambo masters come to my academy, the Freestyle Fighting Academy.
It was more by accident that we managed to get him to teach an amazing leg lock seminar. Lot of weird and funny behind the scenes stories as well, LOL!
This sambo master was a UFC veteran of the old school - Oleg Taktarov!
He showed this leg lock from the bottom half guard which is super sneaky and easily done after going for a sweep, check it out