Based on the description you provided, you are located in the bottom row of a standard QWERTY keyboard. If you reach straight down from the home row, the left pointer (L4) finger would typically be used to type the letter directly below on the bottom row.
In this case, if we look at a standard QWERTY keyboard, the left pointer finger (usually used for the "F" key in the home row) when reached down would be used to type the letter "V."
So, the answer is:
V