courts side by side, and the etiquette of stray balls
Since tennis courts are laid side to side and played on by hard-hitting but fallible humans, errant shots are always going off sticks’ frames and net-posts and even fences and bouncing and rolling into other people’s territory.
Context
The physical fact of shared court-space and the small social machinery it requires. "Courts are laid side to side and played on by hard-hitting but fallible humans," so mishit balls constantly "rolling into other people's territory," obliging the etiquette of suspending play and shooting them back. The regimen produces bodies powerful and error-prone enough that their stray shots keep invading the neighbors — an embodied fact of the practice courts. (That Hal and Axford are "constitutionally incapable" of asking a neighbor for their ball back is communication-solipsism's; landed here is the court-physics/etiquette.)