Can't select spline for symmetry in sketch

[android111]

I'm trying to create symmetrical "shoulders" on part of an object and can't select the spline once the Symmetry tool is picked:

I thought I'd simply be able to choose the spline & the vertical axis somehow, but can't seem to figure this out...

[rushabhthakkar_910]

@android111, I was able to mirror it.

Could you share your file..?

[jeff_strater]

2 possible causes that I can think of offhand:

1. that spline is not in the active sketch.  How many sketches are in this design?  If more than one, try toggling visibility of the others to see whether that spline is in the sketch you think it is
2. it is a 3D spline.  Somehow, one of the control points got moved off the sketch plane.  Symmetry and Mirror only work on 2D geometry.  To see if this is the case, select the spline, right click.  Do you see "move to sketch plane" in the context menu?  Then your curve is 3D.  Move To Sketch Plane should fix this.
   

[laughingcreek]

are you trying to use the symmetry constraint-

fo this one both sketch articles have to be present to apply the constrain, ie, you have to have already drawn the second spline.

or the mirror command-

this one draws the second article for you , and then applies the symmetry constraint.

I'll insert the obligatory warning against using mirror and symmetry in sketches here. 

[android111]

I'm able to mirror it, too, but I'm asking about the Symmetry tool.

[android111]

Definitely active sketch, definitely planar... it extrudes normally... hmmm...

[android111]

I guess mirror's what I'm looking for.

What issues are there with using these?

[jeff_strater · Accepted solution]

@android111 - I just tried this myself.  And... you are correct.  The symmetry constraint does not allow splines (either fit point or CV splines) to be selected.  I suspect that this is intentional, but I'm not certain of that.  You can Mirror, as you've discovered.  I suspect that it is too hard to force a spline into symmetry, because they can have different numbers of fit or CV points, etc.