  As this passage indicates, the Mohists regard fa (models) as similar to tools used to guide and check the performance of skilled tasks, such as sawing a square corner or drawing a straight line. Fa are objective, reliable, and easy to use, so that with minimal training anyone can employ them to perform a task or check the results. Fa alone do not ensure success, nor do they erase the distinction between the skilled and unskilled — or between the virtuous and those still acquiring virtue — but for most of us they at least ensure that we will do better than we would without them.