Template:\sandbox/doc
Usage
Returns "/sandbox" if the template detects that the page where it is transcluded is a subpage named "sandbox" (i.e. a sandbox page); otherwise it returns nothing.
This can be useful to e.g. switch the version of a template used in its /doc[umentation] to the version in its sandbox (by replacing {{{template_name ... on the /doc page with {{{template_name{{{\sandbox}}} ...) when that documentation is transcluded on the template's sandbox page.
This is the documentation page, it should be transcluded into the main template page. See Template:Doc for more information.