Now drill a hole through the stick, with the grain, and the stick of your motor base and pass the tube holding the propeller shaft through both. To make this look shipshape, round off the edges. A great advantage of this stick is that it enables you to mount the propeller as far as you like from the frame, thus preventing it from striking. [Illustration: Showing An Excellent Way Of Fastening The Propellers To The Framework.] In mounting the propellers above or below the frame, you will need similar supports. The blocks should measure half an inch in width by one and a half inches square and should be cut with the grain of the wood running lengthwise. The hole for the propeller shaft is drilled near the top, and the block is securely fastened to the frame. It will be found a good plan to mortise the frame slightly in order to make the joint perfectly rigid, even in the face of a bad smash-up. Many boys merely glue the stick in position and bind it securely to the motor base with fine strong thread, and paint it with glue or shellac to hold it in position. These blocks may be fastened either above or below the frame or at the sides. In mounting the propellers, bear in mind that a position above the planes tends to drive the aeroplane downward, while the thrust exerted below tends to throw the aeroplane upward. The builders of model aeroplanes differ as much as to the best position of the propellers as the designers of man-carrying machines. Excellent models have been built with the propellers in either position. It is obviously impossible to lay down a rule for all models, since the properties of the planes vary so widely. A very simple and efficient support for the propeller shaft may be made of metal to correspond to the motor anchorage. Procure a sheet of heavy tin—a piece of sheet aluminum is still better—one-half inch in width and three inches in length. Now mark off a one-half inch, one inch, two inches, and two and one-half inches, and bend over the ends at right angles, as shown in the accompanying drawing. This support may be nailed or screwed rigidly to the end of the motor base, and a hole for the shaft of the propeller drilled through the two uprights. The propeller must be mounted so that the blades will, of course, be free of the base. The size of the support may be altered to suit the frame. In case you are using a heavy propeller, say an inch blade, the metal must be heavy enough to resist the pull of the propeller. The forward ends of the motors may be held by a cross piece cut from a sheet of aluminum six inches in width and two inches in depth, which is bound rigidly to the end of the motor base with shoemaker’s thread. Aluminum suitable for this purpose costs about fifteen cents a square foot, and is soft enough to be cut with heavy shears.