A sushi press is a box with a lid used to make layered sushi (oshizushi).
The box is usually made of wood, but you can get them made of plastic.
Soak wooden ones in water for 10 minutes first before using, then wipe dry.
Then, wipe the insides including the top with the weak vinegar solution called tezu. Put your layers of sushi ingredients in, then press down with the top.
Them remove the pressed sushi from the press and cut into even pieces
After use, wash the box with warm soapy water, then let air dry completely, then store in plastic bag.
Line a terrine or loaf pan with straight sides with plastic wrap. Make your layers. Cover with plastic wrap. Weigh down with a heavy object for 15 minutes or so.
In Japanese, called “Oshiwaku” or “Oshizushihako”.