Every 4x4, 4x6, and round log in a CedarWorks playset has the heartwood of a tree at its center, and that's the source of its remarkable strength. The sapwood around the heartwood dries more quickly than the heartwood and sometimes undergoes a process called "checking".
This natural phenomenon, which produces separations on the surface of the wood, is common to all wood species. Checking does not pass through the heartwood itself, however, or compromise structural integrity in any way. A familiar example of how heartwood remains unaffected by checking is the common telephone pole, which withstands constant stress and continual assaults from nasty weather. Then there are all the post & beam barns throughout the U.S. and Canada, many of which have stood for hundreds of years despite large checks in their framing timbers.
Most of the checking in your playset will occur within the first several months and will subside when the wood has adjusted to its new environment. Rest assured that your set is still just as strong and safe as ever. And please feel free to call us if you ever have any questions.
Multiple checks leading to the center occur only at the very end of a 4x4. Even if the checks converge and form a "through check" it will be limited to the end and will not affect the strength of your playset.
Checking is likely to occur near drilled holes. Yet, the center of the wood remains intact, and bolts and ladder rungs are still tight and secure. Structural integrity is not compromised.