some knots can be tied with mittens but ''untieing'' those same knots with mittens is even harder, a good many knots can be ''slipped'' (with the end doubled back) to make it very easy to untie with or without mittens, knots such as the tautline/the bowline/the second half hitch of a double half hitch, can all be ''slipped'' by passing the end through doubled (as can any knot where the end of the string is used to finish knot) and those knots simply fall apart when that end is pulled to release knot, that is also how the evenk knot works, for example two lenghts of string/rope can be joined by using two bowlines that are both slipped, simple to untie with mittens, even the fisherman's knot commonly used for joining two lengths can be finished by ''slipping'' the ends to make untieing easier (the fisherman's can be more fiddly to tie though with mittens)