Tubing

Tubing is a process by which a player creates a "tube" that is air tight and disallows any liquid (Lava or Water) from entering it. The process begins by digging a hole four spaces wide straight down. Eventually water will be encountered, the process continues however the player builds a stone walls (one brick thick) to his left and right and fills up liquid filled area underneath him with a soft square like sand or mud that can easily be mined with a silver or gold pick. This tubing allows all liquids to be released into the tube at the appropriate time, allowing for massive water transport or obsidian harvesting.

Note: Since patch 1.0.6, blocks can no longer be placed directly in lava. Sand can still be dropped in from above.