Cook rice according to your rice cooker instructions. If you don't have a rice cooker that tells you how much water to add, most packages of rice will have instructions on the bag, usually 2:1 water to rice ratio.
Meanwhile, place Portuguese sausage slices in a nonstick skillet. No oil is needed. Fry until browned on both sides.
Place musubi maker on top of one sheet of seaweed (See picture above). When rice is done, place roughly 1/3 cup of cooked rice inside the maker. When in doubt, put in less. You can always add more rice later.
Use the musubi maker's plunger to press the rice down. Your rice should create a layer somewhere between 1/4-1/2 inch tall, depending on how stuffed you want your musubi. Take plunger off, but leave the maker in place.
Place two slices of Portuguese sausage in maker.
Add another layer of rice and squish down with the plunger as before. This time, leave the plunger on top of the rice and pull the mold off. Then take off the plunger as well. You should be left with a nice rectangle.
Fold both edges of the seaweed over your rice/sausage block. If the seaweed doesn't want to stay wrapped, you can dab your finger into some water and press on the edges to seal them shut.
To make clean slices, it's best to wait for the musubi to cool down a little. Slice each rectangle in half for two large musubi or in fourths for four snack size musubi. Musubi is best eaten day of, but can be refrigerated and reheated in a microwave.