How do I add guide lines in Zero Block?

You can use the following shortcuts:

• Command + H (Mac) / Control + H (Windows) to add a horizontal guide;
• Command + Shift + H (Mac) / Control + Shift + H (Windows) to add a vertical guide.

You can also set the guides from the context menu (there dots in the upper-right corner). There you can hide or show guides, as well as add new ones.

To delete a guide, click the small cross icon located on the guide line.