A sushi rolling mat (巻きす, makisu) is a flexible mat of bamboo splints tied together with cotton string, used to shape cylindrical sushi rolls (maki). The mat compresses and guides the roll as it is shaped without crushing the ingredients.
Plastic wrap technique
For rolls with nori on the outside: lay the mat flat, roll normally. For rolls with rice on the outside (uramaki, inside-out): cover the mat with plastic film before use to prevent rice sticking. The film also makes the mat easier to clean.
Pressure and motion
Roll the near edge of nori over the filling using fingers to tuck and compact, then roll the mat forward in one continuous motion while applying even downward pressure with both palms. The mat shapes rather than compresses — too much force breaks apart the roll.