A standoff for mounting panels such as glass panels in architectural applications include a plurality of parts that are first mounted to the panel and are then used to identify the locations for the anchor fasteners in the support structure or to locate the anchor fasteners as they are driven into the support structure. One configuration includes a bushing that defines a through opening. The bushing is placed through an opening the panel to be mounted. A barrel defining its own opening is then placed on the portion of the bushing that extends from the panel. The through hole of the bushing is aligned with the opening of the bushing such that an anchor fastener can pass through the bushing and the barrel into a support structure to which the panel is to be mounted.