Here’s Richard Miscovich from “From the Wood-Fired Oven”
If an oven is overfilled and the loaves touch during oven spring, the result will be a crust marked by underbaked, doughy sections, referred to as baisure or kissing crust.
Of course, with some breads — think cinnamon rolls — a kissing crust is desirable. But, the problem of baisure makes loading loaves into an oven an important skill (that is, if your oven can fit more than a single loaf). Often I’m loading the oven at some ungodly hour when my spine is still a bit tetchy from being asleep, and the oven itself is dark, so it’s easy enough to make an error with the spacing between loaves.