These were the take-off and landing pits, the drydock and construction pits of the shipyards. Spaceships, like sailing vessels, were never designed to support their own weight unaided against the drag of gravity. Normal terran gravity would crack the spine of a spaceship like an eggshell. The ships were built in deep pits, standing vertically in a network of catwalks and construction grids, braced and supported by anti-gravity screens. They took off from similar pits, riding the anti-gray beams upward like motes mounting the vertical shaft of a searchlight until at last they reached the Roche Limit and could thrust with their own jets. Landing spacecraft cut drive jets and rode the same beams downward into the pits.