You know that moment at the end of a long, awesome day when it comes time to sort out gear...and suddenly everything looks exactly the same?
After too many times of getting my gear mixed up with my climbing partners, I started marking mine with two dots of good nailpolish that doesn't flake off. How do you mark your gear?
After years of not climbing I recently became a BSA climbing instructor. We usually use "company gear" that belongs to the Scout Coucil but inevitably you wind up with bits and pieces of your own gear mixed in. Each of us has a particular color or pattern we mark hard gear with. It might be a single color or strip of patterned tape or a particular sequence of colors.
Soft goods can be tougher as you shouldn't mark them with any dye or ink not recommended by the maker of the gear. And for sure anything with any solvents, including nail polish and most markers, is a no-no. Sharpie makes a water based laundry marker called a Rub-a-Dub that should be safe for any soft goods, though.
I use gaffers tape. It doesn't leave behind residue, it's strong, and you can buy it in different colors. I used to use electrical tape. However, it leaves sticky residue if/when it wears out and falls off which is a big reason why I switched to gaffers tape.