Now the revealing part:......
First trick: Look carefully at the thing that hides the cutting parts.It is not made to cover his body,instead to separate the body in half.It is there to actually to protect Criss from any harm
Second Trick: The cutting blade is not coming too deep because his legs are under the hanging table well place in a folded position
Third Trick: The table is having a special door to put his legs under the table
Conclusion: The spectators that you see is not strangers ,the show has been prearranged with the people standing out there(like most of his tricks). The legs you see on the table is just a structure made out of some kind of material and he secretly put his legs under the table while he pretends to lie on the table.The camera doesn't show his legs while he is lying on the table
Originally figured out by KeygenX