These are four puzzles also known as 'Slitherlink'. For each puzzle, only consider the numbers that have a particular orientation, so use all the 'right way up' numbers in one puzzle, all the 'upside down' numbers in another, and so on. The numbers represent the number of lines that surround that cell, and each loop looks like a letter. The first letter is the 'right way up' one, then rotate anticlockwise by 90 degrees each time to get to the next letter.