Using a clipboard fill can be much more convenient than the pattern fill since you don't need to create a pattern beforehand. Select the marquee tool - you can use any marquee type for this, in this example we'll use a rectangular one.

Select the region you want to use as a pattern.

Press , select 'Edit', then select 'Copy' to copy the selection to the clipboard.

Press , select 'Edit', then 'Deselect' to remove the marquee.

Select the fill tool and press to open the settings.

Choose 'From Clipboard' from the 'Fill Style' menu.

When you are finished with these settings, press the 'Done' button.

Press and release the spacebar or on the region you want to fill.