If the dogs are "tied", do not try to pull them apart as this could cause damage to either dog. The male's penis swells so that he can stay inside the female to ensure his sperm will enter, in order to conceive. Her vagina's walls clamp on his penis and she relaxes the muscles and lets him go when she is ready.You have to let them be (or best to hold the female) until they unlock. This can be anywhere from 5 min to 1 hour. Do not pour water on them, get the hose, or try to yank them. You just have to wait it out. The female decides when it is time.