How to constrain an assembly to the XZ axis?

[sarkadi]

Say I have a shelf in a room, however when I move it around it ends up floating if I'm viewing it at an angle, so I want to constrain it flush to the floor, which is the XZ axis.  Is there a quick way to do this?  I'm trying to do the constrain -> mate -> select floor, select bottom of shelf legs -> apply, but it gets an error.  But I'm wondering if instead of trying to select the floor, I can just easily tell it to stay on the XZ plane. Thanks

[brent_e_barbour]

I don't see why not.  Just open the "Origin" folder in your browser under the main assembly.  You can constrain to the planes, Axis, or point.

[A.Acheson]

If your getting an error likely you need the flush constraint or the opposite of what you tried at first. This would normally be the case if you have already used constraints and there is only one combination left. If the constraint will work without error you should get a preview of the correct position if you have the preview switch on. You could just as easily use flush/mate constraints to the origin planes or indeed place an angle constraint if you do not want to fix the position.
As regard quick ways you could use some ilogic for this but it really depends on how many you do daily as there is potentially a  big learning curve on this automating especially with constraints. 

[sarkadi]

Thanks, so what would be the steps for making this constraint?

[brent_e_barbour · Accepted solution]

In the "Constrain" command, you can select a Work feature from the browser such as a plane, axis, or point instead model geometry or in combination with model geometry.  Every assembly and part have an origin folder full of X, Y, and Z 0,0,0 work features for this purpose.  You can also create your own work features for constraining.  I'm sure you can find a tutorial video online on how to do this if you need a visual, but play around with it yourself first.  It's easy to figure out.