Schlage FB50N V SIE 619 FB50NVSIE619 SN Siena Entry Combo Single cylinder deadbolt operates with a key on the exterior and a thumbturn on the interior Deadbolt features biggest bolt diameter for maximum kick-in resistance and hardened steel deadbolt core that spins to resist saw attacks Knob is field reversible to allow it to be used on both right handed or left handed doors Snap and Stay design on deadbolt cuts installation time in half Larger deadbolt thumb turn is easier to grip