The invention resides in an adjustable packer apparatus for adjustably adjusting a clearance space (2) between members of the apparatus and when in use between at least two support members (4), (12). The adjustable packer apparatus comprises at least one first and one second planar member (30) and (32) and adjustment means (34). The planar members (30), (32) are configured and spaced from each other and each include a body with at least one aperture (49), there through whereby one planar member (30) is adjustably movably attachable by the adjustment means (34) through alignment of the at least one aperture (49), of one planar member (30) to the other planar member (32). The adjustment means (34) includes at least one bolt having a head (64) at one end, adjusting end (84) at the other end and outer thread body (62) movably attached to and protruding from the rear or second planar member (30) and the first or front planar member (30) has a threaded member (66), (104) protruding therefrom, wherein the bolt is threadingly engaged with the threaded (member 66), (104). The at least second planar member (32) is attachable to one of the two support members (4), (12) which provides a stiffer or less flexible support than that provided by or for the first planar member (30). In use the first and second planar members (30), (32) can be called front and rear planar members. Adjusting the adjustment means (34) causes one planar member (30) to move in a direction perpendicular to its planar plane (as attachable to one support member (4)) with respect to the other planar member (32) which is attachable to the other support member (12,) to reduce or increase the clearance (2) there between the planar members (30), (32), whereby during adjustment ie rotation initiated from/about adjusting end (84) either clockwise or anti-clockwise, of the bolt (62) which threadingly moves and travels through the threaded member (66), (104) while a head end (64) of the bolt (62) is held positionally there about but is rotatable there about, rear planar member (32), and (wall 12), is immovable or not readily deformable in comparison to the front planar member (30) and jamb member (4) or base member (76), to cause the front planar member (30) with its threaded member ((66),104) with the jamb member or base member (76) to move accordingly to either narrow or widen the clearance gap (2) between the front and rear planar (members 30), (32) and between the jamb member (4) or base member (76) and the wall (12). A method of installation is also disclosed.