Abstract: For assemblying a plurality of extruded aluminum strakes with their edges formed for interconnection by plastic key joints, thereby to form a side wall for a transit vehicle, a panel support is formed to support a required plurality of the strakes in completed conformation. Clamping mechanism then squeezes the strakes laterally to a designed assembled width, thereby interlocking the joints, and opening up a key-forming passage lengthwise within each joint. An adhesive injecting manifold is mounted for reciprocation toward and away from one end of a panel on the support, with a nozzle on each of a plurality of outlets of the manifold for sealed engagement, one with each panel joint passage. The manifold inlet has controlled connection to a supply of pressurized, flowable, hardenable, key-forming compound for injection into the joint passages, with flushing means arranged for alternate connection to the nozzles for flushing out the nozzles and manifold after use.