This trimming tool is made from steel, oil hardened and tempered. It is rust proof and durable for professional potters. This kind of trimming tool is suitable to trim a thin and tight foot ring. In order to best trim a tight foot ring, you have to make the blade as sharp as possible. This tool is much easier to sharpen than commercial loop tools.
To sharpen the blade, use a fine file or a piece of sandstone, hold the trimming tool firmly at about 30 degrees, and file the blade horizontally. Do not change the filing angle or holding angle during filing or the blade will not be straight. If you file too much, the tip of blade may bend to other side. Constantly check both side of the blade with finger tip to make sure it is straight. If it bends to the other side, file the back side slightly to make it straight. Do not use high speed motor driven grinders to sharpen this tool as they may damage the blade.
In order to trim pots smoothly, you need to know how to keep the blade in the best condition.