Yes but I think most people use both.
You can use either thumb to touch the space bar.
i think its your thumb 2nd Answer: The thumbs are used only for striking the space bar . . . the "B" key is struck with your left index or pointer finger.
If you mean what finger should you use to make a space while typing then i would say either your right thumb or index finger next to it.:)
That really depends upon the kind of work that you want to do. I could type without a thumb if I wanted to (I only use it to hit the space bar, which I could do with other fingers if I wanted to). And there are lots of jobs which consist mainly or entirely of typing. But I wouldn't want to work in a shipping and receiving department without a thumb.
using the space bar.
Use the Space bar.
Press the space bar
space bar
Press the space bar! (while you are holding it).
you have to press the space bar
press the space bar
press the space bar