Nowadays robots are playing an important role in various aspects of science and industry. In this course, mobile robots stand in a special place. Autonomous Guided Vehicles, for short AGV, as an example of mobile robots have been widely utilized in industry. Knowing this fact, researchers from the early stages, have considered motion planning of mobile robots and developed various solutions for this sort of problem. These methods fall into two general groups: offline and online path planning. In this research, an offline method for navigating robots is presented in general and then it is applied on a non-convex (L-shaped) mobile robot. To do so, at first several paths are constructed by use of different approaches. Afterward, three different criteria are introduced and the computed paths are ranked up on these criteria by use of TOPSIS method. Having these paths in hand, a corridor for navigating the robot is built. The main advantage of the corridor is providing a safe and collision-free platform for navigating all types of robots namely our desired robot which is complicated from geometrical perspective. Keywords: Mobile Robots, Path Planning, Non-convex Robot, Guiding Corridor, Inward Minkowski, Slices of Minkowski.