Preheat the oven to 350 degrees F. Grease and line a 13-by-9-inch baking sheet.
Break the sheets of graham crackers on the perforated lines into smaller 1-by-3-inch rectangles, and lay them out on the prepared baking sheet as close together as possible, covering the entire sheet.
Mix the butter and sugar in a saucepan over medium heat. Once the butter and sugar mixture comes to a bubble, add the chopped pecans and stir together.
Pour the mixture evenly over all of the crackers. Bake for 10 minutes and then cool, about 30 minutes. Break or cut into pieces to serve.