and the outside positions can instead be named as left and right. The defense's halfbacks have been renamed cornerbacks (CB), a fitting term given that they play at the edges or "corners". The term has no spurious indicator of the depth at which they are positioned in the defensive backfield. Finally there are shown two safeties. In this case they are distinguished as "free safety" (FS)—also known as "weak safety"—and "strong safety" (SS). The strong safety is on the side following the strong (tight end) side of the balanced offensive line (see above), and has responsibility for covering (guarding as a pass receiver) the TE, while the free safety has no such coverage assignment. However, the coverage played by defense does not always easily allow assignment of such distinct names for safeties. A formation with more than two safeties could have them described by their relative geometric placement—outside, shallow, deep, etc.-but such is not general practice; however, see the discussion of the "nickel" below. The offense is diagrammed in what was for some time referred to as a "pro set"-- "set" indicating that the players are stationary, although one back may go in motion from it. This particular version is said to have a "deuce", "flank" backfield. From the description above of the straight T, this formation can be seen to be derived by splitting one end and moving the halfback on the opposite side to a flanker position. Instead of "SE" and "FL" for those positions, however, we see "WR", for "wide receiver". In the 1960s, teams would distinguish between split ends (e.g. the New York Jets professional football club's George Sauer) and flankers (e.g. his teammate, Don Maynard) on their player rosters. For a relatively brief period, game rules had been adopted in some codes, requiring different uniform numbers for line players from those of backs, and the position naming distinction carried on for a while after the rules were amended to require only certain sets of numbers for ineligible and eligible receivers of forward passes. It became commonplace for ends to shift into backfield positions and vice versa. By the 1970s, the common practice changed to refer to flankers and split ends both as wide receivers or, more colloquially, "wideouts"—they play from wide of the rest of the formation. The playing rules still distinguish between ends and backs on offense. There are differences as to the motions,