These leveling knobs help keep your bed level while making adjustments to your bed height. Each knob has a moveable scale that allows you to set a "zero" bed height. Plus, minus signs indicate an increase or decrease in bed height. The scale is non-specific and simply marks position; knobs are set in equal positions to maintain a level bed. Now you can make adjustments to your bed up or down keeping it level the whole time. Remember you can use positions between tick marks as well for even finer adjustment.