A replacement heart valve commissure assembly may include a locking mechanism including a first locking portion spaced apart from a second locking portion in a delivery configuration and configured to engage with the second locking portion in a deployed configuration, wherein the first locking portion is longitudinally actuatable relative to the second locking portion between the delivery and deployed configurations. The commissure assembly may include a first valve leaflet and a second valve leaflet each secured to the first locking portion. A first sleeve portion of the first valve leaflet may be fixedly attached to a first fabric sleeve wrapped around a first leg of the first locking portion by a first filament, and a second sleeve portion of the second valve leaflet may be fixedly attached to a second fabric sleeve wrapped around a second leg of the first locking portion by a second filament.