<SUBMISSION>
<ACCESSION-NUMBER>0000020740-16-000128
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20160303
<FILING-DATE>20160307
<DATE-OF-FILING-DATE-CHANGE>20160307
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>CLARCOR INC.
<CIK>0000020740
<ASSIGNED-SIC>3714
<IRS-NUMBER>360922490
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1130
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>840 CRESCENT CENTRE DRIVE
<STREET2>SUITE 600
<CITY>FRANKLIN
<STATE>TN
<ZIP>37067
<PHONE>(615)771-3100
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>840 CRESCENT CENTRE DRIVE
<STREET2>SUITE 600
<CITY>FRANKLIN
<STATE>TN
<ZIP>37067
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>CLARCOR INC
<DATE-CHANGED>19920703
</FORMER-COMPANY>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>CLARK J L MANUFACTURING CO /DE/
<DATE-CHANGED>19871001
</FORMER-COMPANY>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>BURGSTAHLER ROBERT J
<CIK>0001196471
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-11024
<FILM-NUMBER>161488100
</FILING-VALUES>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_145738079909419.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2016-03-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000020740</issuerCik>
        <issuerName>CLARCOR INC.</issuerName>
        <issuerTradingSymbol>CLC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001196471</rptOwnerCik>
            <rptOwnerName>BURGSTAHLER ROBERT J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>840 CRESCENT CENTRE DRIVE, SUITE 600</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>FRANKLIN</rptOwnerCity>
            <rptOwnerState>TN</rptOwnerState>
            <rptOwnerZipCode>37067</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock Par Value $1.00</value>
            </securityTitle>
            <transactionDate>
                <value>2016-03-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>50.44</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>29874</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock Par Value $1.00</value>
            </securityTitle>
            <transactionDate>
                <value>2016-03-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>5303</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>50.44</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>24571</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Common Stock Par Value $1.00</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>35.66</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-03-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>35.66</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2004-03-23</value>
            </exerciseDate>
            <expirationDate>
                <value>2016-03-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>common stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7500.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>45000</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">In connection with the exercise of stock options due to expire.  Transacted was effected by means of a stock swap (i.e. through surrender of previously owned shares of the company's common stock held for at least six months).</footnote>
        <footnote id="F2">Withheld shares for option costs.</footnote>
        <footnote id="F3">Contains shares from multiple grants: 3/26/07 - $31.96 - 7500.0 - expires 3/26/17; 3/31/07 - $35.55 - 7500.0 - expires 3/30/18; 3/23/09 - $25.31 - 7500.0 - expires 3/22/19; 3/23/10 - $35.11 - 7500.0 - expires 3/22/20; 3/22/11 - $44.07 - 7500.0 - expires 3/21/21; 3/27/12 - $49.35 - 7500.0 - expires 3/26/22</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Michelle J. Pearson, By Power of Attorney</signatureName>
        <signatureDate>2016-03-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
