Agency pass-through security types covered include, but are not limited to: fixed and adjustable rate single family residential pass-throughs, GNMA and GSE multifamily pass-throughs, Puerto Rico GNMA Serial Notes, and GNMA HMBS. The dollar roll is a critical component of pass-through trading strategies and a vital cause and effect of demand (a hot roll feeds on itself). In general, the stronger the demand for a particular coupon from a particular agency (or sometimes, the tighter the supply), the more likely dealers will be short and have to. 21. Development of the Pass-Through Market The pass-through is the most common structure for mortgage-backed securities. A pass-through issuer acquires mortgages either by originating them or by purchasing them in the whole-loan market. Many mortgages with similar characteristics are collected into a pool, and undivided ownership interests in the pool are sold as pass-through certificates.