Selby's Spiral Shelf Support is a great solution for shelves that become unstable over time due to slight warping, wear and tear, or poor installation.
During or long after installation, a simple turn of a screwdriver can adjust the support 2mm up or down. Pins are 7mm long and are available in 1/4" or 5mm diameter. Standard color is Clear. Available in Light Brown, Dark Brown, Gray and Black on special order.