How to create horizontal guidelines vs vertical

Trying to learn SK Make 2016 (x64). I can’t create horizontal guidelines that stay in place. I have tried dragging the TM tool off of the inference point but when I click again, I get a vertical guideline or the newly created line disappears. Is there some setting that I have not found, or is this some problem with the programming? (I read the post of Oct '14 and note that StanAccy did not seem to have his problem solved.)

You can create guides (the infinite lines) by dragging the ‘Tape Measure’ tool off of an edge or another guide, not of an endpoint.
Be sure that displaying guides is enabled. There isn’t any other setting that you could have missed.
But I’m suspecting you have a display issue with your graphics card plus its driver.
Try menu Window > Preferences > Opengl > disable ‘Use hardware acceleration’ and restart SketchUp!
See if now you can see all guides that you create.

Try this combination Line and Guide Tool:

Thank y’all for the most helpful suggestions. I am embarrassed to admit that I was using the Tape Measure tool wrongly. In order to have a horizontal guide, one has to click on the nearest horizontal surface and move the mouse vertically until the proper point is reached, then click again. A horizontal guide line will form and follow the mouse to the second click point.

My error was finding the midpoint of a board, setting a guide point, and trying to get a horizontal guideline from that. That method is wrong and will not work.

But in my defense, it is not mentioned anywhere in the Help or the Instructor areas.

Your first sentence gave me the clue that I needed. Many thanks.

Nice tool addition. Thanks for the suggestion.

Setting a horizontal guidepoint IS noted in the Keyboard Shortcuts printout. I just forgot or missed it since I first started out.