  We introduce a method of constructing a forcing along a simplified
$(\kappa,1)$-morass such that the forcing satisfies the $\kappa$-chain
condition. Alternatively, this may be seen as a method to thin out a larger
forcing to get a chain condition. As an application, we construct a ccc forcing
that adds an $\omega_2$-Suslin tree. Related methods are Shelah's historic
forcing and Todorcevic's $\rho$-functions.
