The stanley ht350 fat max pro hammer tacker has a retractable integral knife blade which allows for easy cutting prior to fixing or tacking in place designed specifically for roofings insulations underlay and felting applications etc with bottom staple loading for quick and easy loading and a captive staple pusher can use the following blades 11 921 11 937 11 987 fires heavy duty g type staples 8 10 and 12mm