A key feature of load-holding cylinders is the integrated mechanical locking mechanism, which distinguishes them from cylinders that rely on a separate external valve. 

In a common design, this mechanism includes a mechanical locknut or a specialized sleeve that engages and clamps the piston rod when hydraulic pressure is removed. This design provides a positive, fail-safe lock that ensures zero movement and eliminates the risk of drift or unintended retraction. 

The lock can be manually or hydraulically operated to release, allowing the cylinder to move again when needed. The mechanical locking system removes the dependence on the hydraulic circuit to maintain a position, which is especially beneficial for long-term holding applications or in environments where hydraulic leaks are a concern. Some models are double-acting, with a hydraulic return, to provide faster and more controlled retraction. 

The cylinders are typically made from durable, corrosion-resistant materials to withstand harsh environmental conditions. Integrated sensors can also be included to provide feedback on the locked or unlocked status.