Schlage SC1 vs SC4 vs SC20 vs S123: Which Lishi Tool Do You Need?
Schlage residential cylinders are the most common lock a North American locksmith meets, and Lishi makes several tools for them. They do not overlap cleanly: SC1, SC4, SC20 and S123 are four different keyways, and two of them also exist in a left-groove version.
This page explains what each Schlage tool in our catalogue is listed for, and the checks that decide which one to buy.
Short version: the keyway stamped on the cylinder or the key decides the tool - not the cut count. SC1 and SC4 are different keyways even when both read the same number of cuts, and the -L suffix marks a left-groove version of the same keyway.
The Schlage tools side by side
| Tool | Keyway | Cut count as listed | Notes from the listing |
|---|---|---|---|
| SC1 | SC1 | Not stated | Residential pick tool |
| SC1-L | SC1, left groove | 5 | Left-groove version of SC1 |
| SC4 | SC4 | 6 | Residential decoder and pick |
| SC4-L | SC4, left groove | Not stated | Left-groove version of SC4 |
| SC20 | SC20 | 6 | Door lock, anti-glare finish |
| S123 | S123 | Not stated | Residential pick tool |
Start with the keyway, not the cut count
Two of the tools above read six cuts: SC4 and SC20. If you choose by cut count alone, they look interchangeable. They are not - SC4 and SC20 are different keyways, and a tool cut for one will not read the other correctly.
The reliable identifier is the keyway code stamped on the cylinder face or the original key. Read that code first, then find the listing with the same code.
Left groove versus standard
SC1 and SC4 each have a left-groove sibling in our catalogue, marked with an -L suffix: SC1-L and SC4-L. The prefix is the same keyway; what changes is the groove position on the blank, which is why one version will not slide into the other's cylinder.
Pick up the key with the cuts facing up and look at which edge carries the groove - then compare it to the listing photo. Buying the wrong groove version is one of the most frequent mix-ups we see in the Schlage range, because the tool number is identical apart from the L.
Door, deadbolt or both
Residential work splits across knob and deadbolt cylinders, and the listings say which position each tool is built for. SC20, for example, is listed for the door lock. Confirm the position you are working on, because the same keyway can appear on more than one lock body.
Three checks before ordering
- Read the keyway code from the cylinder face or the key - SC1, SC4, SC20 or S123.
- Check the groove side against the listing photo to decide between the standard and the -L version.
- Match the cut count to the listing: 5-cut for SC1-L, 6-cut for SC4 and SC20. Do not assume an unstated cut count matches the one you were told.
Common mistakes
- Buying SC4 for an SC20 cylinder because both are 6-cut.
- Ordering the standard SC1 when the key is left-groove.
- Using a knob tool on a deadbolt because the keyway matches.
Frequently asked questions
Is SC4 the same as SC20?
No. Both read six cuts in our listings but they are different keyways.
What does the L mean in SC1-L?
It marks the left-groove version of the SC1 keyway. The prefix is unchanged; the groove position is different.
Which Schlage tool do customers ask for most?
SC4 and SC1 are the two profiles we get asked about most often. Use the keyway stamp to choose between them rather than the tool number you heard.
Where can I see all Schlage tools together?
Our Schlage collection lists every Schlage profile we stock; the wider residential collection adds Kwikset, Master and mailbox tools.
Schlage tools in this comparison
Related reading: cut types explained · compatibility guide
