Daisy-chaining extension cords is a process for connecting two extension cords together when one extension cord isn't long enough. Daisy-chaining extension cords is fine when the cords are of a large-enough gauge to support the extra run, but can be limit the amount of power to the tool (and even be a fire hazard) when the gauge of extension cord is too small.
String out the two extension cords to be daisy-chained, so that there are no kinks in the cords.
Insert the male end of one cord into the female end of the second cord.
Align the two cords about a foot beneath the connection. Make a large loop with the two cords, then push the connection through the loop and tighten to make a loose knot.
Plug the male end of one extension cord into the power outlet.
Connect the tool to be used into the open female end of the daisy-chained extension cord.
Tying a knot in the cords at the point of the daisy-chained connection will help keep the cords from pulling apart.
When extending extension cords, always use larger gauge cords than the tool would normally require. The larger diameter wire will help ensure that the extra cord length will not cause a voltage drop below the level required by the tool.