Which sense do you use to read the Braille system?

Explanation

The Braille system is the most widespread and international alphabet for people who are visually impaired. It was devised by the Frenchman Louis Braille in 1824. He was inspired by a military system invented to allow soldiers to read orders without light. The letters in the alphabet are raised dots, which are felt with the finger tips. The number and placement of the dots within the basic rectangle of six dots in two columns.