|Because I am a little unorganized about my sewing, and don't want to spend a fortune on special sewing storage cases, I tend to re-use old shoe boxes or tupperware to store my sewing notions.
This quickly became a problem for my spools of thread and half-used bobbins. Many of my spools of thread are only wound on a cardboard cylinder, with no notch to catch the end of the thread. All the thread would unwind and create a massive snarl of thread in the box.
Now I keep a roll of either Scotch or electrical tape in the tip-out accessories box of my sewing machine. (or the top drawer of my sewing desk). Whenever I change thread colors or bobbins, I cut off a small square and tape the loose thread directly on the spool or bobbin case before throwing it back in the thread box.
If I am switching to a spool that is already taped, I often just take it off the new spool I am using and use it to tape the old one before throwing it back in the box.
I find electrical tape leaves less residue, but I haven't had any problems even with a little stickiness from scotch on my bobbins. The first time I use scotch, I stick it first to my jeans, to take off some of the glue.
Important! Don't tell your family that you have roll of scotch tape in your sewing machine, or it'll be gone faster than cheap laptops on black friday ;)