Apparatus for supplying moisture to an envelope, having a body portion and a flap portion, the apparatus comprising, a substantially solid-rectangle-shaped pad (70) made of a material capable of upwardly transferring fluid by capillary action, means (72) for supplying fluid (74) to the pad, the fluid supplying means including a source (76) of supply of fluid, the fluid supplying means including an elongate well (80) having an elongate substantially rectangularly-shaped base wall (82), the well including a fluid inlet tube (90) depending from the base wall and removably connected in fluid flow communication with the fluid supply source, the well including a pair of elongate substantially rectangularly-shaped and oppositely-spaced side walls (84), the well including a pair of substantially rectangularly-shaped and oppositely-spaced end walls (86) extending between the side walls, the side and end walls extending upwardly from the base wall, the well including a plurality of upright posts (88) located at spaced intervals longitudinally of the length of the base wall, the posts dividing the well into an elongate receptacle (92) for receiving the pad and an elongate fluid inlet channel (94) connected in fluid flow communication with the inlet tube, the pad removably mounted in the receptacle, means for supporting the well, the supporting means including a bracket, and the well removably slidably connected to the bracket to facilitate disconnecting the well therefrom.