Sometimes it’s not possible in diagrams or charts, that a line goes over another one. To not let this crossing look like a real connection of the two lines, we can let the top line go over a gap in the bottom line. It would require to calculate the intersection of the lines.

However, there’s an easy way: draw the firsts line normally, then draw the top line with a bit whitespace around. Or the top line first thicker and white (or background color), then again thin and black (foreground color).

The probably easiest way in TikZ is: draw a “double” line (TikZ manual, 15.3.4 Graphic Parameters: Double Lines and Bordered Lines). Originally, it gives two parallel lines with space in-between filled by a color. But we want to get a single line. Solution: a double line in white, the gap between them filled in black. This results in a black line with white space around.

Many words, short and simple code example:

This way, double distance is the width of the actual black line, while line width stands for the white space on each side.

Use it such as:

It can look like:

Or:

When I defined an image as a TikZ node, I easily create and use a flipped version: I define a mirror style that does a reflection for me:

As my original style was defined this way

I simply override the image style by adding the mirror style:

This way I can get a diagram with a focus to its center:

In diagrams, I need to include images, such as symbolic icons or photos of actual hardware. I defined a generic TikZ style with two arguments: the name of the image, and the desired width. The height comes automatically with the same aspect ratio.

For the final node style, I apply this style plus adjustments such as actual node width and x or y separation:

All style definitions above go into a \tikzset command, separated by comma, plus many more global styles I need:

This way I get photos with annotations for larger physical diagrams: