The short answer
Most shattered door and rear windows are tempered glass. Once tempered glazing fractures, it loses its integrity and breaks into many pieces; resin cannot reconstruct it, so replacement is required. A small surface mark that has not fractured the pane should still be inspected before anyone calls it repairable. Scratches, pits and chips do not all respond to the same process.
Some vehicles use laminated side or rear glazing, which can remain together after cracking. That does not automatically make windshield-style resin repair suitable. The ANSI repair standard cited for auto-glass repair is written for laminated automotive glass in the windshield, and a vehicle manufacturer or repair-system provider may impose different limits elsewhere. Side glass must move correctly in tracks and seals, while rear glass may contain defrosters, antennas, cameras or other components. A technician should identify the glazing from its markings and VIN, assess the location and depth of the damage, and check the applicable service information. Replacement is the cautious recommendation when damage affects visibility, edges, operation, retention or embedded features.
