From Google search:

  1. A box containing sand, especially one kept on a train to hold sand for sprinkling on to slippery rails.
  2. A virtual space in which new or untested software or coding can be run securely.

Original photo supplied by Andy Anderson, who wrote, when asked for a picture…

The sort of sandbox I’m thinking of isn’t really a visual thing: it’s a play area for application developers to compile and run quick tests. A virtual space in which new or untested software or coding can be run securely. As used by CLS AD folk! I’m surprised you didn’t already have it!

The internet mostly has pictures of children playing in receptacles filled with sand, but I prefer the railway version, used for applying sand to slippery rails:

Thanks Biggles.

Original source of photo: https://commons.wikimedia.org/wiki/File:Sandkasten_BR103.JPG

BTW. Sandkasten is the German for Sandbox. Sandkasten bauen means “build a sandbox”, which we will treat as sandbox building.