When you want to bring the kids running, there are few things more effective than a pan of cookies fresh out of the oven. Ideally, there will always be a wire rack nearby to cool them on. However, that's not always the case. Sometimes you might be baking in an unfamiliar location, where such niceties aren't available. Sometimes, especially near the holidays, there just aren't enough racks for all the cookies. Fortunately, there are many ways to improvise.
Why a Rack?
Cookies are among the most delicate of baked goods. The difference between overbaked, underbaked and just right can be a matter of a few seconds either way. The heat of a sheet pan will continue to bake the cookies even after they're removed from the oven, so it's important to transfer them as quickly as possible. A cooling rack speeds the cooling process by allowing air to pass beneath the cookies. It also keeps the cookies crisp by allowing steam to evaporate from underneath the hot cookies, rather than trapping it and making the cookies soften.
If a proper cooling rack is not available, it's often possible to improvise by drawing one from another location. For example, if you bake your cookies on the middle rack of your oven, you might pull out the second rack to cool your cookies on. The rack from your toaster oven or countertop convection oven also makes a fine substitute. In a pinch, you can even use the grill from a barbecue. Cover it first with paper towels or brown paper, to prevent any food residue from getting onto your cookies.
Often, the kitchen will contain other items that can be used to improvise a substitute for a cooling rack. Does the silverware drawer contain several pairs of chopsticks? Line them up, and cool cookies on them. If you have bamboo sushi mats or place mats, those also make excellent substitutes. So do wire, bamboo or wicker trivets. In each case, the surface has air spaces underneath to prevent condensation. If you're uncertain how sanitary a given item is, cover it first with a clean kitchen towel or paper towel.
Flat surfaces are less than ideal, because they do permit a certain amount of condensation to develop. You can counter this by covering them with brown paper or a clean kitchen towel, to absorb the moisture. Transfer your hot cookies carefully to a cool sheet pan, a plate or a countertop, to bring them down rapidly to room temperature. If all else fails, turn a plate upside down on the counter and balance your cookie sheet on it. The plate will absorb some heat from the pan, and it will raise the pan above the counter to allow air circulation.