Some jet transport aircraft use the main landing gear doors to hold the gear in the retracted position...instead of specific uplocks.
The Lockheed TriStar is so equipped.
After the gear is retracted, the landing gear selector handle (on the instrument panel) is placed in the OFF (central) position.
In this scenario, the hydraulic pressure is removed from the landing gear actuator, and the gear rests on the mechanically locked doors.
Some airlines utilized the procedure wherein when the landing gear is lowered, placed the selector handle first to the UP
position, then immediately DOWN, to avoid the large THUMP that would otherwise be noticed by passengers, if the gear selector handle was moved from OFF directly to the DOWN position.
It does indeed work as advertised.