Sherline 3/8 in Boring Tool Holder (included with P/N 2250Quick Change Tool Post and Holders). Each holder has a knurled brass knob that allows you to easily adjust the height of the tool tip. Changing tools is simply a matter of releasing the locking screw, sliding out one tool holder, sliding in another and relocking . If you find your jobs require a lot of tool changes, this timesaving accessory will make your projects that much more of a pleasure.