The design of the Nunc TripleFlask does not allow for mechanical scraping. However, cells are easily harvested using protein digesting enzymes, such as trypsin, collagenase, and Pronase or by using non-enzymatic dissociation solutions.
The following is a document link regarding culturing techniques for Nunc TripleFlask:
https://assets.thermofisher.com/TFS-Assets/BID/Technical-Notes/culturing-technique-nunc-tripleflask-technical-note.pdf