Two primary applications spring to mind: pie crusts and southern biscuits (though there are dozens more in baking and probably hundreds in cooking). What makes lard so desirable for pies and biscuits? Simply, because unlike butter, it’s all fat. Butter contains roughly 12% water, and that water causes trouble in a pie or biscuit dough. What sort of trouble? Gluten. As I’ve written so many times before, water + flour + agitation = developed gluten. Developed gluten is stretchy stuff that makes crusts tougher, and is also responsible for the shrinkage that happens when a pie crust hits the heat.
There are precautions one can take to minimize both the creation and impact of developed gluten in a pie crust (the semi-complicated technique on the right side menu is specifically designed to defeat gluten). However it never hurts to stack the proverbial deck in one’s own favor by cutting out, to as great a degree as possible, the main culprit in gluten formation: water. Replacing half the butter with lard (or shortening) is a time-tested technique for creating crusts and biscuits that are tender (due to reduced gluten) and also flaky (because even a little water can dampen a crust’s texture and/or ruin its crispiness).
Why not go hog wild and use 100% lard in your crusts or biscuits? You certainly can, and many people, especially poorer people, do. However lard, like shortening, has one big drawback: it doesn’t have much flavor (leaf lard barely has any flavor at all). That’s why many bakers have historically split the difference between the two, sacrificing some of lard’s flake for the flavor (and color) of a part-butter crust. But by all means, feel free to experiment.