Fascine mattresses (Geotextile)
Fascine mattresses and cribs that incorporate a geotextile have a different shape to that of the classic version made exclusively from willow. Geotextile adds the extra sturdiness needed for sinking the mattress into deep, fast-flowing water at the right location. In many cases, a covering of willow is not necessary. Van Aalsburg imports the geotextiles itself. A special sewing machine is used to sew them together. Partly as a result of this, fascines and cribs are available in any size.
Sinking of the fascine mattress
The faggots are attached to ropes or towing lines. The towing lines are first attached from the fascine mattress to a float. A crane ship or crane pontoon tows the float via the ropes until the fascine mattress has reached its destination.
The top end of the fascine mattress is sunk using a sinking beam and the rest by dumping rocks onto it. Winches pull the sinking beam up again in readiness for the next action. Sinking of the mattress involves the work of a specialist and requires the experience of a sink boss.