An implantable adjunct for use with a surgical stapling instrument is provided. The implantable adjunct comprises means for allowing a clinician to determine the degree of skew, if any, that the adjunct may experience when implanted into a subject with a surgical stapling instrument. The implantable adjunct comprises one or more reference systems configured to be compared to the staples, the edges of the adjunct, and/or any other adjunct elements by a clinician once the adjunct has been implanted into the subject. The one or more reference systems comprise references that define one or more zones of the adjunct. A clinician can visually determine what zone, or zones, of the adjunct the staples have satisfactorily, and/or unsatisfactorily, purchased the adjunct.