How to select checkboxes in Gmail via keyboard?

Question

I noticed that I can use the arrow keys to move a cursor up and down in my inbox like you see in the 11th email in the list having a blue index to the left of the item:

In normal checkbox I navigate to via some tab order I use the spacebar to check/uncheck the currently selected item.

How do I do likewise in Gmail?

I'd like to avoid using the mouse for selecting non-contiguous items.

Answer 1

Here is a list of keyboard shortcuts: https://support.google.com/mail/answer/6594

But you use the x key to select a message

Answer 2

1. Go to your Gmail account.
2. Go to Settings (Gear symbol).
3. Check option Keyboard shortcuts on.
4. Save the changes.
5. Use x to select/deselect conversation.

Source: https://support.google.com/mail/answer/6594