Draw the inclined straight line which will be the middle of heart, then we draw heart a little narrow and sideways we give volume. Do not erase a straight line, it it to be useful.
Further draw a keyhole and a bolt.
We draw a key, at the beginning of a keyhole from thin, then extends, it is connected with prospect.
We erase the auxiliary line and unnecessary, here such has to turn out the lock from heart by a St. Valentine's Day.