A row filled edge to edge is a course, it locks into the wall and clears the site. Lay several at once for a bigger payday: 2 = SPAN, 3 = BUTTRESS, 4 = RAMPART. In a 1v1 race, everything past a single course dumps rubble rows into your rival's site, and their rubble comes right back at you. Clear lines to cancel incoming rubble before it lands.
Finding you a rival on the UFCR multiplayer server.
The crew's on break. Nothing's moving.
The stack tipped over the top of the site.