This section outlines the four dimensions of codes that comprise the APEX coding scheme—physical, intellectual, social, and emotional. For each dimension, we provide a brief overarching description. We outline a general definition for each code but we leave the “specifics” section blank to allow you to customize the coding scheme to your exhibit(s). Examples of specifics that have been filled in for other exhibits are provided for guidance. We include a set of “keywords” for each code as well as a set of notes and guiding questions (where relevant) to aid you in filling out examples specific to your exhibit for each code. We recommend observing participants engaging with your exhibit after reviewing this coding scheme and using your observations to fill in the “specifics” section with examples. Specifics may need to be iteratively revised and added to during the early stages of observation. After establishing the specifics of the coding scheme, two analysts should establish inter-rater reliability before moving forward with the analysis.