Rusted Jack
This is not a SmartJack. SmartJacks are steel, with a galvanized coating that won't rust.
Sagging Subfloor
Subfloors can sag is the crawl space pillars are too far apart, or if they sink into the ground.
Not a SmartJack
SmartJacks are designed to protect the largest investment you will ever make (your home). This is not a SmartJack.
SmartJack System
These SmartJacks won't sink or rust.