Structure Block

Hello ! Do you know if there is a way to redefine the "center" of a structure ? When we define a structure with a structure block, I think we need to put the structure block at the corner of the structure (if we can put it at the center of the structure tell me), so because we need to do that, my structure is generated on the structure block, so sometimes the real structure is flying. If you don't understand something (it's possible I'm not english) tell me ^^