如图所示，梯子AB靠在墙上，梯子的顶端A到墙根O的距离AO为24m，梯子的底端B到墙根O的距离BO为7m，梯子顶端A下滑了4米到C，底端B滑动到D，求BD的长。---**Chart/Diagram Description:** * **Type:** Geometric diagram. * **Main Elements:** * A vertical line segment labeled AO represents a ladder leaning against a vertical wall. * A horizontal line represents the ground, meeting the wall at point O, forming a right angle (implied corner). * Point A is on the wall (vertical line). * Point O is at the base of the wall on the ground. * Point B is on the ground, located to the left of O. * Point C is on the wall, located below A. * Point D is on the ground, located to the left of B. * A line segment CD represents another position or object connecting point C on the wall to point D on the ground. * The ground and wall surfaces are indicated by hatching. * A horizontal line extends leftwards from the origin, and a vertical line extends upwards from the origin. * **Relative Position and Direction:** OA is a diagonal line segment. CD is another diagonal line segment. O is the origin/corner. B and D are on the horizontal line to the left of O. A and C are on the vertical line above O. C is below A. D is to the left of B.