A flapper is a piece of netting with a mesh size at least equal to that of the codend, fastened inside a trawl, in such a way that it allows catches to pass from the front to the rear of the trawl but limits their possibility of return.
Zaklopnica je kos mreže, ki ima oko vsaj tako veliko, kot ga ima vreča, in je pritrjeno na notranji del vlečne mreže tako, da omogoča prehod ulova iz sprednjega dela v zadnji del vlečne mreže, vendar preprečuje, da bi se vračal.