Keep, Change, or Test the Existing Key and Rekey Path
Separate key retention, a new cylinder, mechanical override, emergency function, and app access before replacing a deadbolt.
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“Keyless” does not tell you what happens to the key already in the door. Before buying, separate the mechanical key path from app, keypad, fingerprint, and voice access.
Ask four different questions
- Will the current key still work? An inside retrofit may retain the outside cylinder, but the exact lock and installation interface still matter.
- Will the new cylinder accept the key you want? “Rekeyable” does not mean compatible with every existing key or keyed-alike plan.
- Is there a mechanical key or inside operation? A touchscreen or app is not a physical override. A manually turned thumbturn, such as Lockly’s Lyro Lasta description, is also not the same as a keyed cylinder.
- What happens during a power or connectivity problem? Check the exact model’s documented backup path and test normal operation as its manual directs.
Kwikset’s support distinguishes its current KW1 SmartKey cylinder from a newer SC1 cylinder: the cited SC1 cylinder takes SC1 five-pin keys, not KW1 or SC4 six-pin keys. That is a Kwikset-specific distinction, not a cross-brand keyway rule. Aqara describes the U400 as having a mechanical key and a rekeyable design; confirm the exact package and cylinder before relying on either feature.
Make a key plan
Write down the current keyway, who needs a working key, whether the exterior key must stay, and how the inside lock will operate. If a replacement uses a new key, plan who receives copies and whether the cylinder can be keyed alike under the exact manufacturer’s instructions. For a rental or shared property, confirm permission and access requirements before changing the hardware.
After installation, verify the physical key and inside operation using the model’s normal instructions. If emergency operation or local egress requirements are unclear, pause and ask the manufacturer, property manager, or applicable authority. For the hardware path, see retrofit or replace; for local fit and variant checks, see USA and Canada documentation.
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