Following on from another thread, can I make a plea here.
Firstly, coupler-leads are designed to walk multiple dogs ON THE LEAD. On no account should dogs be allowed to run together off lead, coupled together. Can you imagine the trauma if 2 dogs ran into a toddler with a chain between them? I post this following an incident where my own dog became entangled between a pair of couple-chained dogs earlier this year. Their owner was luck to escape with his balls. My dog was scared shitless.
I also worry about dogs on a long extendable lead, for similar reasons. These leads can become a spaghetti like mess. I wouldn't want to disentangled one from around another dog, less still a child. I have seen severe bruising on an adult's leg because of such an incident.
Please take care.