When multiple vuser to perform tasks at exactly the same time then insert the rendezvous point to emulate the peak load on the server.
The "Rendezvous point" could be inserted at the moment, when exactly you wanted the Vusers to act simultaneously.
You can find a start and end Transaction, in the script if you have generated.
Insert the rendezvous point, just before starting the transaction.
This implies that, all the Vusers are asked come and reach at the point before starting the transaction, and perform the operation at that particular time.