used when replacing a fig3 type louver 15 however the original system may be provided with removable louvers if so desired the removable louver system comprises a downward extending bushing 24 which extends into the bottom rail 12 and an upward extending bushing 24 which extends into a recess 38 of the louver 15 a spring bias plunger 36 is shown biased by spring 37 through the recesses in bushings 24 to remove the louver 15 it is only necessary to extend a wire or object through the drain hole 27 to compress the plunger 36 upward against the spring 36 until it is free from the recess 26 in the lower bushing 24 when this occurs the whole louver 15 may be slipped sideways and completely removed enabling the louver to be replaced or repaired having already explained that the universal link bar 21 is preferably made in two pieces and that the operation of the spindles and bushings may be reversed it will be understood that a small bushing 39 may be inserted through the top edge 17 of the louver 15 to provide a frictionless recess for a guide pin 41 which extends from a simple universal link bar shown in the form of a rectangular structure 42 refer now to fig5 showing an enlarged top view of the preferred embodiment universal link bar 21 which comprises the aforementioned modular bar 35 and the novel bushing 32 which is provided with a plurality of expandable prongs 33 which extend through the uniformly provided apertures or recesses 34.