The hand extension robot orthosis (HERO) glove was iteratively designed with occupational therapists and stroke survivors to enable stroke survivors with severe hand impairment to grasp and stabilize everyday objects, while being portable, lightweight, and easy to set up and use. The robot consists of a batting glove with artificial tendons embedded into the glove's fingers. The tendons are pulled and pushed by a linear actuator to extend and flex the fingers. The robot's finger extension and grasp assistance are automated using inertial measurement unit signal thresholds. Five stroke survivors (Chedoke McMaster Stroke Assessment - Stage of Hand 1-3) put on the HERO Glove in 1-3 minutes, with assistance. The stroke survivors performed significantly better on the Box and Block Test (2.8 more blocks transferred, ) while wearing the HERO Glove than when not wearing the glove. Four stroke survivors could only transfer blocks while wearing the HERO Glove. The HERO Glove enabled these stroke survivors to more fully extend their index finger (an increase of 97.5°, ) and three of five stroke survivors were better able grasp a water bottle. Therapists and stroke survivors suggested increasing the HERO Glove's grip force assistance and valued the glove's portability, lightweight design and potential usefulness in assisting with task-based therapy.