Levelling Block
A levelling block is a block, usually stackable, placed under a wheel or a jack to raise that point. It is used to close a coarse height difference and is no substitute for fine adjustment. Industry practice is to reposition the vehicle if more than three layers are needed on top of each other.
The blocks have an interlocking toothed structure; when stacked they form a ramp or a platform. Used under a wheel they raise that axle end, and used under a jack they close the distance the jack cannot reach.
- Layer limit: as the stack gets higher, lateral stability falls. If more than three layers are needed, choose another spot.
- Full seating: the wheel must sit in the middle of the block, not on its edge.
- Cracking: a cracked or deformed block is not used; it carries the risk of sudden collapse under load.
- Under the jack: the block must be horizontal and in full contact; the block under the jack is the point most open to sliding.
Blocks and an automatic system are not alternatives to each other but complementary. If the ground slope is too large for the system's stroke margin, the right approach is to make the coarse correction with blocks and leave the rest to the system. A levelling block is also no substitute for a wheel chock, which prevents sliding.
Context in which this term is used: Guide to automatic RV levelling