Pemko 145B 36" Mill Brass Water Return Interlocking Threshold
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When measuring to determine the proper height for a threshold you would want to measure from the sill to the underside of the door and then make appropriate accommodation for any unusual job site conditions and then a very small margin between the top of the threshold and the bottom of the door perhaps 1/16”.
Regarding the interlock hook strip that piece is always included when an interlocking threshold is ordered and does not need to be specified separately unless of course you want a hook strip that is of a different configuration, such as an L style hook like the Pemko 66A as seen here:
than the standard J style hook that's included.