Hi Vladimir<br><br>Thanks for the explanation.&nbsp; I didn't understand the semantics of override before&nbsp; your explanation.&nbsp; I get the gist of what you are saying and it explains the ambiguity errors I was getting in my toolset before I added these statements. The override&nbsp; for searched-lib-generator makes sense.&nbsp; What about prebuilt?&nbsp; What's the motivation for:<br><br>generators.override builtin.lib-generator : xyz.prebuilt ;<br><br>Assuming $(xyz) = gcc , is gcc saying that it doesn't want the unix rule for prebuilt but rather builtin.lib-generator.prebuilt ?<br><br>Thanks for your help.&nbsp; I'm sure there will be another fledgling toolset developer who will benefit.<br><br>Regards,<br>Mark<br>