Abstract: A non-displaceable, self-righting shim for use in any application where critical alignment is required of adjacent vertical elements. The shim presents an elongated central opening including a large upper portion and a small lower portion, and a slot having an exit end communicating with the central opening and an entrance end at the perimeter edge of the shim. The weight distribution of the shim relative to the large upper portion is such that the shim will hang in a normal upright position with the small lower portion and the slot below the large upper portion. The arrangement assures positive placement of the shim once installed; avoids loosening and fall-off of the shim which may be caused by thermal expansion and contraction of the shimmed element and/or by vibrations associated with the adjacent vertical elements; and eliminates the need for holding the shim in position while securing the fastener.