Common used functions are placed within libraries in the SQABasic directory. Files ending with ".SBH" have the public interface they give to other libraries and scripts. Files ending with "SBL" contain the execution of the public interface and private functions.
You use them by containing them in your testscript or in another library. Though, never ever contain a .SBL-file into your script or library, instead contain the header file only (.SBH) otherwise you run into cyclic redundancy problems and the compiled SBX file growths for nothing.
Example
GOOD:
'$include "axCommon.sbh"
FORBIDDEN:
'$include "axCommon.sbl"