Purchase or download a direct box circuit schematic from an Internet resource. The schematic is your guide to the construction of the direct box. There are various online resources that explain what the symbols mean if you have no experience reading circuit schematics.
Use your circuit schematic as a parts list, and purchase the electrical components that are represented in your schematic and a blank circuit board. Purchase the electrical components in an electronics store or Internet retailers.
Insert your components into your circuit board. Bend the connectors to keep the components in place. Orient the components as displayed in your circuit schematic.
Solder your components into place by heating the connectors with the tip of your 25-Watt soldering iron at the joint of the circuit board and the connector for one to two seconds. Once the component connector is heated, feed a small amount of your rosin-core solder between the head of your soldering iron and the joint. Repeat this process for all component joints.
Use the wiring pencil to draw the connections between components directly onto your circuit board as represented in your schematic. A wiring pencil works similarly to a soldering iron, drawing a thin strip of conductive copper directly to your circuit board.
Use your hand-held rotary tool to cut holes for the input, output and attenuator switch into your project box. Most direct boxes require two 1/4-inch holes for the input and output and a third hole or slit to accommodate the type of switch you purchased.
Place the audio input, output and attenuator switch of your direct box on the inside of your project box. Fix both components firmly in place by twisting the included bolts from the outside.