Description of the different steps

1. Select your part, go to the Tools ribbon, and click on Structures.
2. To hollow your part, select Outer Shell, define a wall thickness, and click on Next. To replace a complete volume with lattices, enable No Outer Shell.
3. In the following menu, set your preferences and click on Next.
   1. Choose Structure: Allows you to choose a unit cell structure, or add another STL file to use as unit cell by clicking on Add.
   2. Structure Dimensions: Allows you to define the dimensions of the unit cells.
   3. Advanced Options/Spacing: Allows you to define the spacing between the bounding boxes of the unit cells.
   4. Advanced Options/Start Position: Allows you to define the starting position of the lattice.
   5. Advanced Options/Angled Growth: Allows you to define an angle for the unit cells.
4. To add drain holes, add perforations using the following page.
   1. Perforation size: Allows you to define the inner and outer radii of the perforation caps.
   2. Use Notch: Creates an indentation that facilitates re-assembly.
   3. Keep Subtracted Parts: Creates new STL files out of the perforation caps, so that they can be assembled with the part after printing.
   4. Total Clearance: Allows you to leave space for the glue you will use for reassembly.