Hello,

I want to ask how to rotate imported object to make it horizontal or vertical. When I'm rotating it by dragging one of the corners I can set it to "more or less" horizontal position. Is there any way to do it by for example picking two points and automate process. I attach photos to visualizate what I mean. Thanks for answers. 

Put in a horizontal guide, when in rotate mode drag the pivot point to for example the bottom left corner of the bar, where you want it horizontally aligned. Drag it till the pivot point snaps to the guide. When snapping mode is correct enabled rotate till it snaps. I can make a short gif later - if that description is too vague.

To be honest it's my third day with inkscape. I don't even know how to turn on "snapping mode". I would appreciate if you can make gif for me.

Sorry for that crap gif - but it´s really late: