light hour - the distance light travels in a vacuum in one hour; approximately one billion kilometers. 1  astronomy unit - a linear unit used for astronomical distances. 2  light year, light-year - the distance that light travels in a vacuum in 1 year; 5.88 trillion miles or 9.46 trillion kilometers.
keystone. n. 1. (Building) Also called: headstone or quoin the central stone at the top of an arch or the top stone of a dome or vault.2. something that is necessary to connect or support a number of other related things.(ËkiËstoÊn). n.eystone. n. 1. (Building) Also called: headstone or quoin the central stone at the top of an arch or the top stone of a dome or vault.
PRE-KEYED SHAFTING. TruKey Â® Shafting from Keystone is designed to provide the straightest, most accurate pre-keyed shafting in the industry. We stock keyed shafts in the most common diameters, including metrics, with standard keyways. We can provide pre keyed shafts cut to any length up to 20'.