its axis a driving mechanism preferably a spool is coupled to the drive shaft for rotation therewith whenever the drive shaft is rotated a driven mechanism preferably a guide drum is selectively coupled for rotation to the driving mechanism the spool has the flexible filament wound about it and is coupled to one of the driven and driving mechanisms for rotation therewith the metering mechanism includes a device for rapidly decelerating the rotating drive shaft and driving mechanism together with a device for disengaging the guide drum mechanism from the spool during the rapid deceleration whereby the guide drum is free to rotate a discrete amount relative to the spool in this manner a length of filament is metered from the spool application_number US 1114279 A description referring to the drawings in detail wherein like numerals indicate like elements there is shown in fig1 a line metering apparatus in accordance with the present invention designated generally as 10 the line metering apparatus 10 is used on a flexible filament vegetation cutting device 12 a portion of a lawn mower 14 with which the cutting device 12 is preferably used is shown in fig1 the lawn mower 14 includes an outer housing 16 which is carried out a ground surface by a plurality of wheels one of which is shown as 18 a cross member 20 is attached within the housing 16 the cutting device 12 including the line metering apparatus 10 are attached to the cross member 20 a generally cylindrical shroud 22 extends downwardly from the cross member 20 and has a central opening 24 for receiving portions of the cutting device 12 a flange 26.