As a Mommie to an only child furbaby, I need help with using a Coupler. Going on vacation soon & my daughter is taking her furbaby. Would love to use a Coupler for both. I found this that I have. Is it used as a Coupler? If so, HOW??

lol
I've seen the ones that have the hook attachments on each end, but have no idea how this one works.
Help me out pls.
ps...I would Loooove to have 1/2 doz yorkies
aaaaahhh....maybe one day