Abstract: A sit-up device apparatus adapted to be utilized in conjunction with a door having spaced apart vertically extending surfaces and a bottom intermediate the surfaces. The apparatus is comprised of a frame configured as to be removably secured under the door. The frame includes an elongated base with surfaces oppositely disposed in a fashion as to create a certain compression of the frame when device is extended below the bottom of the door and upon the surface of the floor. The upper surface of the elongated base is configured in such a fashion as to engage the bottom surface of the door, and in combination with a section of material affixed to the upper surface of the elongated base, whose front surface is positioned as to engage the lower portion of the backside wall of the door, the device is aligned and secured in its operative position.