An implicit part of the Howesian school of track maintenance, stone blowing is the injection of measured quantites of 10mm chippings under the sleepers to remove voids and produce a level road.
The FR has the prototype "hand-held" (actually a two man lift!) stone blower, simply a large diesel powered fan. This has a hose attachement into which stones are poured and carried along in the airstream follwoing the Venturi effect - in a similar way to a perfume spray!!
A typical stone blowing team involves an advance man jacking the track, one or two Kangoing in steel square hollow sections to hold the hose in place, one working the hose, one delivering buckets of chippings and maybe a few more helping the whole process forward. The noise of the stone-blower, generator for Kangos and the Kangos themselves mean ear-defenders have to be worm, so all communication is by hand signal. Despite this, when a close-knit team has got going it works like a machine.
Unlike Network Rails satellite linked, CDROM, laser guided machines that pour in stone until a level is reached, the amount of stone is carefully measured in an old enamel pint mug, the quantites calculated by eye using Sighting Boards.