FreeCAD can be extended with the following extensions:

• Showing grid: use following key combinations: g-r¹⁾
• translation + rotation → placement. See a wonderful article here: https://github.com/DeepSOIC/Lattice2/wiki/Introduction-to-Lattice-workbench

• Fasteners http://theseger.com/projects/2015/07/generating-holes-for-countersunk-screws-in-freecad/ and http://theseger.com/projects/2015/06/fasteners-workbench-for-freecad/
• Sheet metal http://theseger.com/projects/2015/06/sheet-metal-addon-for-freecad/