I wanted a simple, inexpensive light for use in an open boat but which could be hoisted if need be for a riding light, and serve for a navigation light under power.

A mustard pot, flex, ‘goo’, two crocodile clips and some stout galvanised wire for the cage, and two bits of cod-line for lanyards, are the essentials, along with a redundant car/motorcycle battery.

Solder a long (Ford &c) car interior bulb to one pair of ends. Drill a hole in the lid to fit the flex, pull through all but 1½” (with the bulb inside!) and seal with ‘goo’. Put on the lid, attach croc. clips and it should light when connected.

The cage is made by middling one piece of wire in an eye, putting another eye half way down the ‘side’ of the jar, and at the lid end (not the bottom), an eye in one end and a hook in the other. If the hook is made well, it can be unbent to remove the lid if need be. A second wire is middled through the top eye of the first and led down the sides with side eyes, and a hook on each bottom end to go round the stem of the bottom eye. A girdle wire is then threaded through each of the four side eyes and twisted together neatly. A blob of solder can be used at each joint. Finally, lanyards are spliced to the eye at each end, lengths to suit, remembering that a rolling hitch to the forestay will hold it up, on a short bit, but it may need a longer lanyard to hold it down and stop it moving too much.