Only in Super Mario Bros 3 you can hold and throw shells holding the b button when you touch them.
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You can't actually throw them up but you can get them in the air for a second or two by jumping while letting go of the shell.
You just jump like you would normally, unless you mean the blocks on the ground and then if you run at them quickly and press down you will get Mario/Luigi to go into their shell and you will rebound off anything you touch. Much like Koopa shells would if you throw them at things.
In Super Mario Bros. 3, in order to throw hammers, you will need to enquire a hammer suit. The easiest place to find a hammer suit is the first toad house in world 6, the ice world.
Run to his back, then take him and throw him (not out of the ring!) Do it 3 times to win.
Jump on top of the an egg, press (B) to grab it, run up to birdo and press (B) again to throw it back.