I assume you mean when two dogs are "tied" post-intercourse. If this is the case, then the male dog will be able to push himself out once the penis has un-swollen. This is a natural process and it can take between 15 to 45 minutes. DO NOT PULL THEM APART, since this will most likely cause damage to the male's penis.
Knotting a dogs penis is not taken literally it is not tying a penis in a knot it is when the dogs penis gets stuck in the dogs vagina and he begins ejaculating
Tying the Knot - 2012 was released on: USA: August 2012
Marriage the correct answer
Tying the knot usually means that two people are getting married.
a tying knot for shoe laces on shoes!
My shoelace has become tangled into a knot. I am tying a Monkey's Fist knot.
The cast of Tying the Knot - 2012 includes: Molly Berg as Janet Rex Davison as Robert
Tying Shoelaces
Getting married.
Mansome - 2012 Tying a Knot 2-122 was released on: USA: 20 August 2013
Knot tying is an ancient art which originated due to practical purposes. Grasses and reeds were and still are used to make strings and ropes which then are connected together in an intersection now referred to as a knot, for a variety of practical purposes.
"Typing the knot" does not mean anything (as an expression I mean). "Tying the knot" on the other hand means to get married.