This book is designed to help the reader to understand better the Biblical concept of doors. The word "door" usually refers to the revolving structure blocking an entrance. An accepted definition might be "the barrier that grants or restricts access to something, somewhere or someone." Its synonyms are words like "doorway, portal, opening, entrance, entry or exit." Although it is quite literal, it is often used as a metaphor. The Bible uses it both in its literal sense and metaphorically. Some essential concepts explored here are: Doors grant or restrict access. Doors may open to new opportunities. Prayer opens doors. Jesus has the authority to open and shut doors.