ARPand#039;s 3923 gutter sealant must be used during the installation of aluminium gutters through the snap fit jointing process in order to ensure integrity in each joint. After lengths and fittings are clipped down into position in the fascia brackets, unions should be fitted at the points where said components meet by placing them at the rear face of the gutter before bringing them down and clipping them at the front.Each aluminium union features two large holes on its base, which are to be filled with this sealant during the installation of aluminium gutters until it reaches smaller bleed holes at the rim of the union.