Various features can be observed on some artifacts that indicate errors in preparation or judgment on the part of the knapper. Identifying these occurrences can assist in forming a picture of the knapper's individual abilities. For example, all knappers occasionally misjudge a blow but indications of repeated poor judgment can denote the work of a beginner or a novice (Bodu et al 1987; Pigeot 1990; Ploux 1991).
The following are some knapping errors and features that indicate poor core preparation or maintenance.