MAKE function documentation -- example of use?

The make function description in the documentation is not described well. It seems to imply that there is a default operation for each system that the system developer can specify somehow, without saying how. I see that there's a FIXME suggesting that we need to document the BUILD-OPERATION option for DEFSYSTEM. It would be nice to have an example that shows how MAKE is intended to be used. Not a super-detailed example, just a quickie to show that this is not a feature in search of a use.... Anyone used this? thanks, r