Zombie Siege? I Have a Construction System

Lin Ye, a construction site manager, wakes up to find zombies smashing through the unit door downstairs. Before they can reach the sixth floor, he welds three steel bars onto the door of his prefab room—the first zombie that lunges is sent flying half a meter, its skull cracking on impact. He builds a half-meter-thick wall of hollow bricks at the stairwell, and a hundred-strong zombie horde crashes against it, bloodying themselves without leaving a single crack. Starting from a leaky prefab shed, he dismantles scrap cars for steel plates, erects a three-meter-high wall, and builds a vertical farm. Those who follow him no longer fight over cold bread—they come home to warm heating and fresh vegetables every meal. — Description from novelcodex.org