Abstract: An aligner including a feature positioned on or in at least one of the buccal sidewall or lingual sidewall of the aligner that is configured to attach to an elastic member. The aligner applies a greater corrective force to a patient's dentition when the elastic member is attached. The feature may include a protrusion in the sidewall with an opening to a space configured to receive and attach to an elastic member hook coupled to the elastic member. The feature may include a through-bore in the sidewall that is configured to receive and attach to the elastic member. The feature may include an add-on hook on the sidewall that is configured to receive and attach to the elastic member. The add-on hook may be positioned on a protrusion in the sidewall. The protrusion may receive and engage with a dental attachment positioned on a surface of a patient's tooth.