SQL Server 2012 :: Insert Rows In A Table

In a t-sql 2012 sql script, I have the following script, that only works for a few records since the value of TST.dbo.LockCombination.seq only contains the value or 1 in most cases. Basically for every join listed below, there should be 5 records where each record has a distinct seq value of 1, 2, 3, 4, and 5. Thus my goal is to determine how to add the missing rows to the TST.dbo.LockCombination where there are no rows for seq values of between 2 to 5. I would like to know how to insert the missing rows and then do the following update statement. Thus can you show me the sql on how to add the rows for at least one of the missing sequence numbers?

UDATE LKC
SET LKC.combo = lockCombo2
FROM [LockerPopulation] A
JOIN TST.dbo.School SCH ON A.schoolnumber = SCH.type
JOIN TST.dbo.Locker LKR ON SCH.schoolID = LKR.schoolID AND A.lockerNumber = LKR.number
JOIN TST.dbo.Lock LK ON LKR.lockID = LK.lockID
JOIN TST.dbo.LockCombination LKC ON LK.lockID = LKC.lockID
WHERE LKC.seq = 2

A normal select statement looks like the following:

select * from TST.dbo.Locker LKR
JOIN TST.dbo.Lock LK ON LKR.lockID = LK.lockID
JOIN TST.dbo.LockCombination LKC ON LK.lockID = LKC.lockID
where LKR.number in (000,001,1237)

In case you need the ddl statements for the tables affected here are the ddl statements:

CREATE TABLE [dbo].[Locker](
[lockerID] [int] IDENTITY(1,1) NOT FOR REPLICATION NOT NULL,
[schoolID] [int] NOT NULL,
[number] [varchar](10) NOT NULL,
[serialNumber] [varchar](20) NULL,
[type] [varchar](3) NULL,
[locationID] [int] NULL,

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