Hi @bitminter, I found large sections of your post in the SAS Survival Handbook from John Wiseman. Are you the author? Could you confirm this please? Thank you!

Dig a hole in the ground approximately 90cm (36in) across and 45cm (18in) deep. Place a collecting can in the center, then cover the hole with a sheet of plastic formed into a cone. The sun's heat raises the temperature of the air and soil below and vapor is produced. as the air becomes saturated, water condenses on the underside of the plastic, running down and dripping into the container. This is especially effective in desert regions and elsewhere when it is hot during the day and cold at night. The plastic cools more quickly than the air, causing heavy condensation. This kind of still should collect at least 55cc (1pt) over a 24-hour period.

This still may also double as a trap. Insects and small snakes are attracted by the plastic. They may slide down into the cone or wriggle underneath it and drop into the hole and then cannot climb out. A solar still can be used to distill pure water from poisonous or contaminated liquids.