louver 420 fig4 accordingly an end cap 900 is constructed of a material having some flexibility such as a thin plastic so that one or more of the side flaps 920 and end flaps 940 can be deflected for attachment to or detachment from a louver 420 fig4 in an alternative embodiment not shown the side flaps 920 or end flaps 940 or both are replaced by a wedge prongs or similar structure extending from the center of the inside face 901 and adapted to insert into and fixedly attached to an end of a louver 420 fig4 the gear 920 is adapted to insert through a groove insert aperture 810 fig8 a b so that the gear teeth 922 engage the teeth of a groove strip 700 fig7 a e a segmented slider 1200 fig1 a e or a stackable slider 1400 fig1 a d within a stile groove 610 fig6 a b fig1 a b illustrate a stile assembly 1100 utilizing a toothed segmented slider 1200 and a tilt control knob 1150 a complete stile assembly 1100 has multiple segmented inserts 800 segmented sliders 1200 and end caps 900 alternatively the stile assembly 1100 has a single stile insert and or a single slider that extend a substantial portion of the stile groove 610 fig6 a b in lieu of segmented inserts 800 and or segmented sliders 1200 respectively the end cap 900 gears engage teeth of the segmented sliders 1200 so that linear movement of the segmented sliders 1200 rotates the end caps 900 and tilts attached louvers accordingly as described in detail with respect to fig1 a e below the tilt control knob.