The Caps Lock key on Mac keyboards often feels extraneous, since it’s easy enough to hold the Shift key while typing multiple capital letters for acronyms like PCMCIA or when you want to shout GET OFF MY LAWN! But if you need to do that on an iPhone or iPad, it’s annoying to keep tapping the Shift key to switch to the uppercase keyboard for each letter. Luckily, Apple has baked a time-saving trick into its onscreen keyboard. Tap the Shift key twice in a row to lock it on, type the letters you need, and tap it again to unlock it. Notice that when Shift is locked on, a horizontal line appears beneath the arrow on the Shift key.
FYI: PCMCIA stands for “People Can’t Memorize Computer Industry Acronyms.”