I want H-shaped girder

[cicatrix]

Has anyone ever figured out how to make something like this?

That segment just won't stick.

[Tex_NL]

Try it with the half size girders with mirror symmetry.

[BagelRabbit]

I would recommend starting with the central segment of the "H," and then put two of the shorter modular girder segments at each end. With a wee bit of fiddling around, you have your "H".

Edit: Ninja'd? Okay. I would also say that it would be best to start with the central segment vertical, and then flip it to horizontal when you're satisfied. That way, the bits of your H can be symmetrical about an axis.

[RainDreamer]

Would be easier with a mod called select root. Stock editor sucks at this.

[capi3101]

I would suggest trying to do what you're doing in the SPH instead of the VAB; it tends to handle mirrored items more readily. Other than that, I have nothing to offer other that what's already been suggested.

[Pecan]

If you are beaten by frustration remember that the editor is changing quite a lot in 0.90, which should be available soon.

[kerbiloid]

There was an old but fine mod  Modular girder system AWT, by kyklop. There are many girder details (mostly just scaled stock ones, but also several additional).

Original link is to kerbalspaceport (so, dead), but maybe you already have it.

Also if you are trying to create something monumental, there is Speedy's Hex Truss System

http://forum.kerbalspaceprogram.com/threads/86388-0-24-1-Speedy-s-Hex-Truss-System

Edited December 6, 2014 by kerbiloid

[The_Rocketeer]

I built a bunch chassis frames in this style for various rovers. As others have said, mirror symmetry is the key, and tho it can be done in the VAB it's a lot easier in the SPH. Those girders can't attach at the middle like fuel tanks do, so you're definitely better off using the smaller ones and reinforcing with struts if necessary.