Why do the 'F' and 'J' keys on keyboards have bumps on them?

I was surprised by this fact too when I saw those bumps after few days of buying my laptop. In fact I called up the shop from where I bought it & the guy took few minutes to cross check if what I said was true.

Later, I googled it to find out few interesting things:

• Most keyboards use a line, but older Apple keyboards used a dot.
• Basic idea of providing the ridge on "F" & "J" keys is to allow people who type without looking at the keyboard to easily find the right keys to put their fingers on (helps in high speed typing). These keys are referred to as the home row.
• In short, they help users correctly position their left and right hand on the keyboard without having to look at the keyboard & merely by feeling those ridges.
• Also, an additional advantage it offers by above mentioned position of your left & right hand on your keyboard is, you should be able to locate the remainder of the keys on the keyboard. It is the optimal placement of hands on the keyboard.

Try it yourself!