More shooting of insulation. The cellulose insulation is blown through the gray tube and out a large diameter nozzle which has two water nozzles (one on each side) spraying into the stream of cellulose to lightly wet it. Starch in the cellulose acts as a glue to give the mass some cohesiveness and hold it in place. That's not to say the insulation is "'glued in" - one could walk up after spraying or now (days later) and pull the insulation right out.