Preheat the oven to 350 degrees F. Line a jelly roll pan (15.25" x 10.25") with aluminum foil and butter well.
Break graham crackers into squares then arrange them in a single layer on the buttered pan.
In a medium saucepan, bring butter, brown sugar, pecans, and salt to a boil over medium heat. Boil the mixture for 2 minutes then remove the pot from the heat. Stir in vanilla.
Pour the hot mixture over the graham crackers. Use a spatula to spread the syrup to the edges of pan to cover the crackers completely. Ensure that the pecans are evenly distributed.
Bake uncovered for 10 minutes until the mixture is bubbly.
Allow the bark to cool completely to room temperature before breaking into pieces.