Double Sided Tape 6mm
Although I now tend to use PVA glue for joining the sides of gift boxes and for most other occasions where I need to stick card and paper together, I would not be without my double sided tape which provides an invisible, professional finish to gift wrapped items. I also much prefer to use tape for sticking ribbon to things and conveniently, the tape and the ribbon are usually available in similar widths. I frequently use 6mm tape with 6mm grosgrain ribbon.
Double sided tape does not soak into fabrics in the way that a liquid glue can do, it sticks immediately and is clean to work with.
Be aware that some tapes are more sticky than others, so it is always worth reading the reviews.