Hello, there! . My name is Muhammad Haris, and I'm a recently graduated Mechanical Engineer. . A few days ago, I happen to receive a drawing with a FRONT VIEW shown below in the image. The only point of interest in this drawing is the yellow highlighted area. In drawing, a thick part line was given which was extending out from a given feature horizontally (Please note that I have replicated the original drawing below, I have checked this view many times to ensure it gets posted rightfully). . Image Link: http://i62.tinypic.com/hwfm3a.jpg . Now my questions are: . 1. What does that thick line represent in the drawing? 2. How and where am I going to maintain that size of 25 mm? . NOTES: The dimensions represented in BLUE COLOR were strictly given in the drawing. The dimension in RED COLOR was calculated by me to estimate the difference in height, and also, note that the tolerances are ignored just for the sake of simplicity. . Image Link 2: 3D View: http://i58.tinypic.com/efh0kh.png . Looking forward to your precious feedback.