December 23, 2005: Apple files a patent application for its iconic “slide to unlock” gesture for the iPhone.

Although the iPhone is still a secret research project at the time, the ability to unlock the device by sliding your finger across it signifies everything Apple wants the iPhone to be: easy to use, intuitive and technologically miles ahead of the competition.

‘Slide to unlock’ sums up the iPhone philosophy

Given everything the iPhone can do, it sounds silly to say that “slide to unlock” was one of the features I remember being most impressed by when I first saw it. Throughout the 1990s and 2000s, as cellphones became ubiquitous, a surprisingly large amount of time and money went into coming up with a solution for unlocking our phones.

These patents bore unwieldy titles like “Apparatus and method for preventing inadvertent operation of a manual input device,” but they all referred to the same thing: how to stop the dreaded “butt dial.”

As the Oxford Dictionary described it, this phenomenon involved an “inadvertent call made on a mobile phone in one’s rear trouser pocket, as a result of pressure being accidentally applied to a button or buttons on the phone.”

The iPhone, of course, didn’t have any buttons on its main display other than the Home button, although there was still the problem of what happened if this was accidentally activated.

Most other companies got around the unlocking problem by using specific sets of button presses, which were unlikely to be made by accident. With “slide to unlock,” however, Apple came up with a method that immediately conveyed the simplicity, elegance and superior touch-recognition technology the company wanted to demonstrate with the iPhone.

As with the best graphical user interface elements, it served as a metaphor for a real-life action — in this case dragging a bolt back across a door to unlock it. The sensitivity of the movement, and the way the bolt would immediately snap back to its starting position if you failed to carry out the gesture correctly, also gave it the kind of “fiddle factor” Apple design chief Jony Ive always likes.

99 problems, but iPhone slide to unlock ain’t is one

With iOS 10, Apple finally consigned the iconic “slide to unlock” gesture to the digital scrap heap. A feature that drew gasps of amazement when the original iPhone was introduced in 2007 found its days numbered when Apple introduced Touch ID with the iPhone 5s in 2013, and Face ID last year.

“Slide to unlock” is still making a difference for Apple, however. The long-running Samsung-versus-Apple lawsuit involves a bitter clash over several key patents, including this one.

As recently as this year — despite the feature being irrelevant to current devices — the patent was still being examined to see whether a) it was something Apple should have been allowed to patent in the first place and b) whether Samsung infringed upon it.

Ultimately, Apple won the verdict last month, with the Supreme Court awarding Apple $120 million, and saying that it would hear no more appeals of the patent infringement case on Samsung’s part.

What was your favorite interface element of the original iPhone? Let us know in the comments below.