The four input fields here are for setting up all pre and post tool change G-Codes. The reason for having "Pre Tool Change", "Tool Change", and "Post Tool Change" instead of just a single Pre Engrave, is that the various Integrex modes need to insert G-Codes between each of these sections. For other machines it is not necessary to use all 4 blocks. For most users all you need to know is all of the G-Codes in "Pre Tool Change", "Tool Change", and "Post Tool Change" will be added at the beginning of your program and the G-Codes in "Post Engrave" will be added to the end of your programs. All of the G-Codes in these for input fields can be saved in a machine file so the settings for several different machines or types of jobs can be saved and recalled later.