A slack technique. Using flaps as speed-brakes in the 737.
The 737 FCTM states: " The flaps are not normally used for increasing the rate of descent".
Elsewhere a paragraph says: "Normal descents are made in the clean configuration to pattern or instrument approach altitudes". I read that as selecting flaps 1 and 5 in level flight at the recommended speed.
From personal observation I would say that on most occasions the flaps are used as speed-brakes because especially on a low drag approach procedure flaps 1 and 5 are invariably selected while the aircraft is still descending towards the outer marker, rather than in level flight at idle thrust. This usually results in the flap selection being made at a speed less than the maximum for the flap position but faster than the recommended flap extension.
Is this just lazy flying procedure or is it perfectly acceptable to ignore the Boeing recommendation that the flaps should be extended in level flight? (except landing flap, of course)