SOLVESPACE is a free parametric 3D CAD tool. Applications include:

- Modeling 3D parts: draw with extrudes, revolves, helixes and
  Boolean (union / difference / intersection) operations

- Modeling 2D parts: draw the part as a single section, and export
  DXF, PDF, SVG; use 3D assembly to verify fit

- 3D-printed parts: export the STL or other triangle mesh expected
  by most 3D printers

- Preparing CAM data: export 2D vector art for a waterjet machine
  or laser cutter; or generate STEP or STL, for import into
  third-party CAM software for machining

- Mechanism design: use the constraint solver to simulate planar
  or spatial linkages, with pin, ball, or slide joints

- Plane and solid geometry: replace hand-solved trigonometry and
  spreadsheets with a live dimensioned drawing