At the ends of the crosspiece drive two nails, allowing them to project 1 or 2 in.  This will keep the rope from slipping off when the rings and swing are raised and lowered.  All sharp edges should be sandpapered to prevent

[Illustration:  Rings and Swing]

the rope from being cut.  A board with notches cut in the ends will make a good swing board which can be removed instantly.  —­Contributed by W. A. Jaquythe, Richmond, Cal.

** Homemade Telegraph Key [283]

[Illustration:  Key and Connections]

A piece of wood, 1/2 in. thick, 2 in. wide and 5 in. long, is used for the base of this instrument.  Two wire nails, each 1 in. long, are used for the cores of the magnets.  Each nail is wound with three or four layers of fine insulated magnet wire, about No. 25 gauge, similar to that used in electric bells, leaving about 1/4 in. of the end bare so that they may be driven into the wood base.  The connections for the coils are shown in the sketch, at A.

About 1 in. behind the coils is fastened a small block of wood, the top of which is just even with the top of the nails in the coils.  A piece of tin, cut in the shape of the letter T, is fastened with two screws to the top of this block, and the end bent slightly so as to clear the top of the nails about 1/32 in.

The key lever is cut from a thin piece of wood, in the shape shown in the sketch, and pivoted in a slotted block which is used as a base for the key.  A piece of bare copper wire is fastened along the under side of the key, as shown by the dotted lines.  A rubber band, passing over the end of the key and attached to the base with a tack, acts as a spring to keep the key open.  A small piece of tin is fastened to the base under the knob of the key.  This is for making the contact between the copper on the key and the wires from the coils, when the key is pushed down.  —­Contributed by W. H. Lynas.

** Protecting Sleeves [283]

Bicycle trousers-guards make excellent sleeve bands when the cuffs are turned back and rolled above the elbows.

** Imitation Arms and Armor-Part VII [284]

The helmets, breastplates and gauntlets described in parts V and
VI can be used in making up a complete model

[Illustration:  Full Suit of Armor]

for a full suit of armor of any size, as shown in Fig. 1.  All of the parts for the armor have been described, except that for the legs.  Figure 2 shows how the armor is modeled on the side of the left leg.  The clay is modeled as described in previous chapters, the paper covering put on, and the tinfoil applied in imitation of steel.  The chain mail seen between and behind the tassets is made by sewing small steel rings on a piece of cloth as shown in Fig. 3.  These rings may be purchased at a hardware store or harness shop.