What is a rectangle?

A rectangle is the portion of the screen between the mark and the point.

Select a rectangle

• C-x SPC: selects a rectangle.

Commands on rectangles

• C-x r k: Kill rectangle.
• C-x r M-w: Copy into kill-ring.
• C-x r y: Yank rectangle.
• C-x r d: Delete rectangle.
• C-x r t string RET: Replace rectangle with string on each line.
• C-x r N: Number lines