This FreeCAD® project builds a custom-size box with removable cover. Specifications are detailed in a spreadsheet and prioritized from the inside since most of my boxes are built to suit the stuff going inside. The main body has a rectangular footprint with rounded corners. The bottom plate can be flush with the sides or overhang the sides forming a brim. This makes a lip to more easily grasp this half of the box when inserting or removing the cover. The cover matches the bottom having the same shape (including a brim) except that the walls have a slightly smaller perimeter in order to slip inside the walls of the main body. The inside dimensions of the box body are freely chosen providing that exterior dimensions lie within the bounds of the print volume. Exterior dimensions are derived from the inside dimensions as are most of the cover dimensions.