Edibles/Poisonous plants and tree identification are always a challenge. I have plenty of books and color plates, but it's always harder in the field. This is one area I'm trying to improve by searching specifically for a few I've studied and if edible (and in season), add them to a meal or snack on.
I've done trapping/snaring with commercial snares and conibears, but I really want to improve the techniques with primitive snares. Honestly, it takes time and we're often on the move and I don't get too many chances.
Knots are a big weak link as well. I know a few basics which can get me by, but there are so many more useful knots I want to try. Even for rock climbing, I just use a few basic ones, but there are a plethora of other knots/uses that I'd like to learn
ROCK6