A transport case is provided for many domestic knitting machines, since they are mobile units, which can be fixed to a working table anywhere. Usually they case provides room for the knitting machine and all it's accessories.
The transport case may have a handle on the outside, so it's actually an oblong suitcase. On the inside the case has special latches, so all accessories of the knitting machine can be fixed safely inside.
Brother knitting machines do not have a designated transport case, but rather a special light metal cover that is attached to the top of the knitting machine with two buckles. Packing a knitting machine for transportation can be tricky, so make sure to read the instructions first.