Circular cuts are generally created by boring a hole using a brace and bit or a drill, then expanding it using a compass or a coping saw or a saber saw. If much of this work must be done, like in cutting a straight cut through floors, it's a great idea to round the end of a crosscut saw, extending the teeth so they form a semicircle. This can be utilized to cut directly on the floor without drilling. A similar outcome can be obtained by bolting half a blade of a circular saw to the base of a steelstrip or an old saw. When the saw cut would be of limited depth, create a fence from two thin strips of wood a bit longer than the saw blade. Bolt the strips together and slip the blade between them, letting the blade extend to the precise depth of the cut. Then fasten the bolts and saw. The fence would prevent the saw blade from cutting any deeper. A knothole is best filled just by cutting a diamond-shaped hole around and cutting the same type of wood with roughly the same grain to fill it. The diamond shape allows for maximum glue area. Mitring operations need careful, precision cutting that is best done using a backsaw. A Stanley No. 1514 is highly recommended. To begin a backsaw cut, create a slight groove on the cut on the waste side, then make a kerf on the waste side of the mark. Be sure to check the accuracy of the angle of the line then hold the backsaw on the whole length of the cutting line. It's best to support the board being cut with a board of scrap wood underneath. After every use of your saw, wipe the blade carefully using an oily rag to keep from rusting. Never cut through nails (use a hacksaw for this) or sheetrock. For painted lumber, use an old saw.