Public Read-Only gives John baseline Read access to every Account, but it does not let him edit Paul ' s Account. When Paul manually grants John Edit access, Salesforce adds an explicit AccountShare entry representing that exceptional access. The new share has a Manual row cause and a Read/Write access level; it does not transfer ownership and it does not convert the existing OWD-derived access into an owner share. Salesforce evaluates all applicable access mechanisms and gives the user the highest effective access, so the explicit manual share raises John ' s effective access on that record from Read Only to Read/Write. The design illustrates the additive nature of Salesforce record security: OWD establishes the baseline and explicit shares can open a specific record further. Ownership remains with Paul, and the manual share should be used only where a deliberate exception to the baseline is required. Study Guide reference: Access to Records - manual sharing, AccountShare, RowCause, OWD, additive record access, and effective access calculation.