Contrary to widespread misapprehension, the tactile aids were not created to help blind people type.
The ridges found on the F and J buttons on a computer keyboard are designed to help users locate the correct keys without looking down.
The reason why only these keys have ridges is to help users place their hands in the optimum typing position.
With your index fingers on the two ridged keys – your left hand covers A,S, D and F while the right covers J,K,L and colon.
Both thumbs then rest on the space bar.
Others adaptations have also been attempted to increase the speed and accuracy of a keyboard user, such as raising the edges of the A,F,J and semi-colon keys.
She in fact registered a patent for raising the edges of the A, F, J and semi-colon keys.