flexwatt wiring

I just got some flexwatt, a power cord, and a wall dimmer switch that I am planning on splicing into the power cord. The power cord is one-directional (it has a larger prong and a smaller one). Which wire does the dimmer splice into? I know there is a "hot" and a "neutral", but I don't know which is which.

I think I found the answer to be the smaller prong is the "hot" wire that the dimmer has to be spliced into. Somebody please correct me if I am wrong.