The block on which this fuse is held is shown in Fig. 22, and is made in a similar manner to the one shown in Fig. 19, except that the metal plates are a trifle longer and are bent up, as shown in the drawing. Thus the mica fuse-plate will be elevated above the block. If the brass or copper used for the binding-post plates is too thin to stand the pressure of the screws when the fuse ends are screwed fast, put a few burrs on the screws below the plates; then the pressure of the screws cannot bend down the extending ears of the plates and make an imperfect contact. Another form of fuse-block is shown in Fig. 23. The same sort of a fuse is employed as shown in Fig. 21, but without the [U] cuts at the ends. The clutches are made by binding brass or copper plates, as shown in the drawing; they should then be screwed fast to a base-block five inches long, one inch and a half wide, and five-eighths of an inch thick. The opening between them should just admit the copper ends of the fuse, and pressure should be used to force the fuse in place so that the contact will be perfect. Still another form of fuse is shown in Fig. 24. This last may more properly be called a non-sparking fuse, for the lead wire is encased in a glass tube, and when it fuses no sparks fly and no small pieces of melted metal can get away from the inside of the tube. The plug is made from a piece of glass tube half an inch in diameter, two metal caps, and a short piece of lead wire. The metal caps are of thin sheet-copper, and are caught at the edges with solder. One end of the lead fuse-wire is passed through a hole in the end of a cap and soldered, as shown at A in Fig. 24. The wire is then passed through the tube and the cap placed over one end of it. This is repeated at the other end and the wire soldered fast. As a result, you will have a glass tube with metal caps held on the ends of the tube, by means of the thin lead wire which runs through the middle of the tube. The base-block to which this fuse-plug is attached is of wood one inch and a half wide, five or six inches long, and five-eighths of an inch thick. Two metal straps are made and screwed fast to the block, and the circuit wires are attached under the copper burrs and held down by the screw-eyes. To place or replace a fuse-plug, unscrew the eyes and raise each strap slightly, so that the copper cap ends will pass under them. A turn or two of the eyes will clamp the plug in position and at the same time bind the circuit wires.