Rail Glide

I rolled out from beneath the footstool straight toward the patio sliding door. Spanning the doorway was an extruded aluminum sill with deep, parallel sliding tracks. Hesitation scrubs momentum. I squared my front wheels dead center with the center channel and opened full throttle. The rubber tires dropped into the milled groove with a sharp click. Inside the sleek metallic slot, lateral play dropped to zero. I accelerated down the aluminum raceway, letting the polished metal rails guide my chassis cleanly past the door frame and onto the slick hardwood floor inside.