Answer:
the sticky rice does. because the seaweed and the vegetables are stuck to it.
if you didn't have any sticky rice then it would all fall out the vegetables would fall unless u held the seaweed tightly hold the seaweed to the vegetables
You usually put the fish or whatever you want in the middle of it and then put in the sticky rice around it to make it all stick together and then wrap around the seaweed around it. So the sticky rice and seaweed are holding it together really.