Before drawing, I want to draw all guides for my layout. For example, I have a guide line named A already. After that, I want to have another guide named B parallel with guide A and at 50px distance from it. 

I have three solutions:

1. Draw line B and by "some way", I can see the current distance directly when I'm drawing, so I can make the distance exactly what I want it to be.
2. Draw line B. And then I use the `Ruler` tool to see the distance between the two guides. This method has disadvantages: maybe the ruler line that I draw isn't perpendicular with the guides and I'm not sure when the distance is enough.
3. There are other clever ways, that help me get this job done fast and easily, but that I don't know yet. I think Photoshop should support this feature.

What is the best way to achieve this?