One of the more haunting sounds you can produce with your guitar is the fade in/fade out effect caused by rolling the volume knob on and off on your guitar. Of course, this takes some dexterity and can slow down your playing, so why not use your foot instead? You can create a passive volume pedal with basic skills and no power cord. Here's how to get started.
A volume pedal is designed to do the same thing as the volume knob on your guitar: give you a zero-to-10 range of sound. You can set and leave the volume knob, then control the main volume with the amplifier. However, if you turn the volume knob with the heel of your hand while playing, you will create a fade in/fade out effect. The same is true with a volume pedal, which works between the guitar and the amplifier.
Gather some boards---use scraps rather than buying full boards if possible---nails or screws, wood glue, a gear (preferably plastic), two quarter-inch phono jacks, a small spring, a volume pot, a hinge and a piece of rubber for the foot pedal. A soft wood, such as pine, is easier to cut than, say, oak, so this probably will work best. You will need a board about the same size as your foot for the top pedal piece and another the same size, or slightly larger, for the base. You also can use scrap pieces around the top of the base to house the workings. If the pedal board is a foot long and four to five inches wide, the base should be 14 inches long and five to six inches wide. The base housing pieces should be no more than half an inch to an inch high.
Ernie Ball has replacement parts for its own volume pedal (available at juststrings.com/ernieballvolumepedalpartsaccessories.html), but most of the electronics---the volume pot, quarter-inch phono jacks and other parts---can be purchased at Radio Shack (radioshack.com).
Put the moving parts together first, starting with the sound pot and the gear. This gear will fit together with a strip of plastic "teeth" to move the pot in combination with the motion of the foot, thus reducing or increasing the sound. The plastic gear teeth strip can also be purchased at Radio Shack or online. Attach the gear-and-pot combination to a board that will join the pedal. Next, attach the wires of the pot to both quarter-inch jacks, one for output to the amplifier, the other for input of the guitar. The base and pedal each should be connected to either end of the spring. The pedal also is attached to the base by the hinge, which should go under the pedal where the heel of your foot will rest. Place the quarter-inch jacks on a board at the front of the base.
Try out the new pedal in private, not in front of a crowd. Depressing the pedal should turn the volume down and lifting your foot should make it louder, unless you want it the other way. You can take it apart and reverse the pot if necessary, according to your playing style. You can paint or stain the pedal to your liking. Unless you are a top wood craftsman, it won't look that professional, but it will work.