[MatthewS]

Not instantly.

It's one of those things you would do once, and then save it as a stencil so that you could reuse.

My method would be to draw two lines. Select the one that should be at an angle and use the angle dial in the Geometry Inspector to set it. Also check the "Allow connections to other objects" checkbox in the Connections Inspector. Connect it to the other line, and you will have an archetype. Paste it into a stencil an you can re-use.