Lockable resource is used in the options block of the pipeline like this: 

options {
       timestamps()
       skipDefaultCheckout()
       lock resource: "Lock_Slave_${SlaveName.split(',').first()}"
       timeout(time: "$JobTimeout" as Integer, unit: "HOURS")
}

There are three jobs in the Jenkins System, which are using the same SlaveName (build with parameters parameter). All 3 jobs are started at the same time. After the first job is started, the other 2 jobs waits for the lock. After the job is done, the two other jobs acquires the lock at the same time. 

Console log job 1:

2019-05-02 10:23:55  Trying to acquire lock on [Lock_Slave_TIS_MainTargets]

2019-05-02 10:23:55  Found 0 available resource(s). Waiting for correct amount: 1.

2019-05-02 10:23:55  [Lock_Slave_TIS_MainTargets] is locked, waiting...

2019-05-02 11:05:58  Lock acquired on [Lock_Slave_TIS_MainTargets]

Console log job 2:

2019-05-02 10:24:52  Trying to acquire lock on [Lock_Slave_TIS_MainTargets]

2019-05-02 10:24:52  Found 0 available resource(s). Waiting for correct amount: 1.

2019-05-02 10:24:52  [Lock_Slave_TIS_MainTargets] is locked, waiting...

2019-05-02 11:05:58  Lock acquired on [Lock_Slave_TIS_MainTargets]

As you can see, the two jobs acquires the lock "Lock_Slave_TIS_MainTargets" at the same time. 

Get in contact with me if you need more information. Thanks in advance!