Usage die

A usage die is used to represent resources that have limited uses but simplifies the record keeping by using a die that is rolled when the associated resource is used to see if it runs out.

The usage die is typically a stepped die and when a 1 is rolled the current die size is stepped down and if reduced to zero (beyond a d4) then the resource is no longer available.

I believe that the Black Hack invented this mechanism and it makes things like tracking rations, arrows and lamp oil far easier while retain the resource play aspect of old school dungeon crawling.