The camshaft is supported by several friction-type bearings, or bushings. They are typically pressed into the camshaft bore in the cylinder head or block.
The typical camshaft bearing is a full round design.
Many late-model ohc engines use split bearings to support the camshaft. camshaft bearings are normally replaced during engine rebuilding.
The old bearings should inspected for signs of unusual wear that may indicate an oiling or bore alignment problem.