You then just wrote on the back of the gift tags, (you had the be careful ,.of course, to cut only the parts of the card that hadn't been previously written on!) and stuck it on the wrapped gift with sellotape,.or, if you were feeling. ambitious,.you used a hole punch to make a hole.in the card and then threaded thin string through.
I hadn't thought about this for years, but remember it was all part of the Christmas fun as a child - thank you for bringing back happy memories!