What kinds of blades are there?

Scrapers are single-sided, double-sided, single-layered, double-layered, three-layered and five-layered electric shavers, including single-headed six-knife rotary, double-headed single-layer rotary, double-ring (three-ring) rotary, single-knife reciprocating, double-knife reciprocating, three-knife reciprocating, sideburns trimming scissors, Panasonic's latest models and four-knife reciprocating.