Fusion Sketch Tools — Quick Reference
A fast lookup for which sketch tool to reach for, matched to what you're actually trying to build. Pairs with the Fusion Sketch Practice — Object Bank — come back here when you're not sure which tool fits the shape in front of you.
For how each tool works, Autodesk's own documentation is the reference. This page is about when to pick which one.
Two habits worth building first
Use the tool that draws the shape, not lines plus constraints. If Fusion has a tool for the shape you want, it will get you there faster and leave the sketch better constrained than hand-drawing lines and forcing them into place afterward.
Aim for a fully constrained sketch. A sketch whose geometry can still be dragged around will move on you later, and it's where stray gaps hide when you export for cutting. Autodesk's Fusion sketch constraints lesson covers how constraints work and what the colors are telling you.
Finding the geometry that isn't constrained yet
Fusion tells you whether a sketch is fully constrained — the red lock icon next to it in the Browser — but not which bits are still loose. On a sketch with any real complexity, hunting for them by dragging things around is miserable, and geometry can look fully black and still have a degree of freedom.
There's a command that just answers the question:
- Turn on the text command window: File > View > Show Text Commands.
- Right-click the sketch in the Browser and choose Edit Sketch — the command only works while you're inside the sketch.
- Type
Sketch.ShowUnderconstrainedinto the text command box and press Enter.
Fusion reports how many elements are still under-constrained and highlights them in the canvas, so you can go straight to them.
Two caveats worth knowing. Autodesk notes that text commands aren't maintained for outside use, so treat this as a diagnostic aid rather than something to build a habit around — it can change or stop working between releases. And it tells you where the freedom is, not what constraint to add; that's still your call.
Autodesk's own writeup, including an Auto-constrain approach and an add-in that does the same job from a button, is How to find under constrained sketch elements.
The two that come up most
Polygon (Sketch > Create > Polygon) for any equal-sided shape — a stop-sign octagon, a wrench's hex cutout. There are three variants, and which one you want depends on which measurement you have: circumscribed (distance across the flats — what a real-world spec like a wrench size gives you), inscribed (distance across the corners), or edge (you define one edge and it builds from there). Autodesk's Polygons in sketches covers all three.
If you've already hand-drawn a polygon-ish shape out of individual lines, the Equal constraint can still force the sides to match after the fact — a useful fallback, but the polygon tools are the direct route.
Fillet (Sketch > Modify > Fillet) for a rounded corner — a phone outline, a skateboard deck. It rounds the intersection of two lines to a radius in one click and stays tangent automatically, which is exactly the "fully constrained, not just close" bar a deliverable is checking for. Don't hand-draw an arc into a corner. Autodesk: Add fillets to sketch geometry.
Quick reference: object → tool
| If the object needs... | Reach for... |
|---|---|
| A straight edge flowing into a curve (ramp, wheel well, guitar body, nose cone) | Tangent Arc (drag from Line, or the dedicated tool) |
| A standalone curve not attached to a line | 3-Point Arc or Center Point Arc |
| A messy sketch with overlapping/extra segments | Trim (Break/Extend for related fixes) |
| Two matching halves across a centerline | Mirror (new geometry) or Symmetry constraint (existing geometry) |
| Evenly-spaced repeated cutouts/notches (mullions, crenellations, windows) | Rectangular Pattern / Circular Pattern |
| A profile nested inside another (frame, case, pane) | Offset |
| A regular polygon (octagon, hexagon) | Polygon tools (Circumscribed / Inscribed / Edge) |
| A rounded corner | Fillet |
| Sides that must match length, drawn by hand | Equal constraint |
Related
- Fusion Sketch Practice — Object Bank
- Fusion Training — Autodesk video walkthroughs
- Exporting Your Design — once the sketch is done