A foldable mounting collar includes first and second collar segments. Each collar segment includes a planar annular segment that substantially subtends a semicircle, a collar flange that, when the planar annular segment is horizontal, extends vertically downward along an inner periphery of the planar annular segment, such that the collar flange forms a cylindrical portion, and two hinge flanges that, when the planar annular segment is horizontal, extend upwardly from each end of the semicircle formed by each planar annular segment. The mounting collar further includes pivot means that hingedly couple pairs of the hinge flanges of the collar segments. The second collar segment can rotate, relative to the first collar segment, through at least a polar angle range sufficient for the mounting collar to fit through an aperture having a diameter defined by the cylindrical portions of the collar flanges when both collar segments are horizontal.