From publisher blurb:
Old School Fantasy Roleplaying: D20 and Roll High for 2nd Edition provides alternate rules for rolling dice results for the 2nd Edition version (2E for short) of the most famous fantasy roleplaying game in the world published from 1989 to 2000.
The guidelines and tables provided in this book are an attempt to accomplish two goals. First, provide rules for using a twenty-sided die (abbreviated D20) for action rolls exclusively for players of 2nd Edition. Second, provide guidelines and tables for changing game procedures that require rolling low for success into rolling high for success instead. These two changes can provide a shorter learning curve for new 2E players and greater convenience for veterans by focusing on one die-type and consistent method for determining success or failure.