Symmetric Between Lines Relation
Picked on three straight lines, two of them parallel, the Symmetric relation holds the third line exactly midway between the two parallel ones, and keeps it there when they move. It is listed as Symmetric between lines.
When to Use It
- Center a construction line between two walls
- Keep a rib or a slot centered in a plate as the plate gets wider
- Build a symmetric part from a center line out
Step by Step
- Open a sketch and draw the pieces (see Lines, Circles and Rectangles). Sketching is part of modeling, which comes with the Pro plans.
- Click Select on the Sketch tab (or press S).
- Click the line to be held in the middle (a construction line is the usual choice), then click the two parallel lines on either side of it. Pick exactly three lines.
- Keep the pointer still for about half a second. A bar titled Add a relation to the N selected opens beside it, with one button for each relation that fits. Click Symmetric. Instead of waiting for the bar, you can right-click the selection and choose Symmetric under Make them, or click Symmetric under Add a relation in the Properties panel.
- A small green square marks the relation on the sketch, and a message says Symmetric added. It stays true as you move and resize; Edit, Constraints lists it. Ctrl+Z takes it back.
Options
| Setting | What it does |
|---|---|
| Picks | Three straight pieces. Two of them must be parallel (the walls, and a part edge can be a wall). The one held midway is the construction line among them; if there is none, the first one you picked. |
| Result | The held line moves to sit exactly halfway between the two parallel lines, and what is tied to it follows. |
| Message | Symmetric added: the line is held midway between the two lines, and what is tied to it follows. Ctrl+Z takes it back. |
| Listed as | Symmetric between lines. |
Tips
- The button in the bar is just named Symmetric.
- If the two walls are not parallel, this choice is not offered. If a construction line and two other pieces are picked, you get Symmetric Relation instead.
- Move or resize the walls and the middle line stays centered. A typed size on the walls moves it too.
- The line held in the middle can also carry other ties, such as a size or an axis for Revolve.
If Something Goes Wrong
- "Symmetric cannot hold together with the relations already there. Nothing changed." Something already placed (another relation, a typed size or a Fix) fights this one. Delete the one in the way from the list under Edit (see Edit Menu) and try again.
- "Symmetric already holds through the relations you have, so nothing was added." The sketch already forces this, so nothing more is needed.
- The button is not in the bar. The bar only lists relations that fit what you picked. Check what is selected in the Selected list of the Properties panel. If the panel says None fits this selection. Pick another point, piece or part edge with it., change the picks.
- "Symmetric applied once: the relation solver could not load, so it will not be kept." The piece moved once but nothing was stored. Check your connection and add it again.