I’ve written a lengthy reply, only to realize that what I’m looking for already exists 
I guess I’m so used to throwing the mouse to where the guide originates, i.e. the ruler, that I never checked whether I could throw it at the other ruler. Hm. Maybe something to consider? As long as I haven’t placed the guide, maybe let me throw it away at either side of the screen?
Below is for documentation. And for laughs.
May I ask how this would help you? Perhaps you just want to check layer alignment, but do not actually want to add the guide with the rulers?
Whenever I need to check alignments, I’m usually not checking alignments of layers, but alignment of content—text, icons, stuff like that. And most of the time, I only need to quickly check whether or not something is aligned, let’s say the baselines of two text layers with different font sizes and line heights or so. So you’re right: I don’t want to place a guide; and layer/frame boxes won’t help either.
I can do what I want, if I hover over the ruler, but the way rulers and guides are implemented in Sketch I need to point my cursor at the ruler, and then stay inside that little area, or else the guide disappears. I guess this is perfect if you just want to perfectly place guides or so, and maybe hide/show all of them. But… I’m old school, hehe, and every other app since Freehand 3 allows me to:
- hover over a ruler
- mouseDown
- drag out a guide
- check the alignment
- “throw” my mouse back to the edge of the screen and… mouseUp
I don’t need to keep my mouse pointer in a 26px area, but I can freely move it around the whole canvas that way. I can move my pointer to my point of interest and check the alignment. Hope that makes sense.
Plus with Sketch, it’s either “see all guides” or “see none”. I can’t even place a guide while the rulers are active but the guide setting is set to “none”. I understand that this may seem counter-intuitive (adding guides with guides hidden), but it’s not about fixed guides for a layout, but just general checking of alignments—a temporary guide. It’s also really hard to get rid of guides in Sketch…
Ok. And since you’re already showing measurements and distances etc. on-the-fly, I thought it might be possible to also have a guide just appear while pressing a modifier. I don’t want to place it on the canvas, I just want to check… alignments.
Hope I made myself clear.
