Thanks for the advice. I googled the coupler leash, and its configuration is what I suspected. While it would help me to control them without a doubt in the case of their getting into certain types of mischief, it would create other issues. I like to keep Yorkie A away from Yorkie B while A is pooping. Also, when they see another dog they really want to meet, they usually start a barking and chasing frenzy. If they cannot get to the other dog (which they usually can't because they are such spazzes the other dogs' owners rarely want to socialize with them), they will take out their aggression on each other. The male is always the instigator of this (yes, he's a wonderful loving pet and he follows me all over the house, but a switch turns on in Gatsby when he sees a strange or neighbor dog and he goes wild). At that point, its best to keep them separated from each other.
How many folks who have 2 (or more) Yorkies tether them together for enhanced control?