Accountig period document lets you to block entry of any transaction between given period. If you want to block all the transaction from every user then you can use it.
Access it from Accounting>Accounting Master>Accounting Period
Closed Document: You can select document from which you want to strict entries. To add more document just click ADD ROW
It will only stopped transaction if it falls between given period. For Example if you defined time period from 1-04-2020 to 31-03-2021 then it will strict entries for that period only after atfer that period you can create entries.
Note: Neither it will allow to create any entry nor it will allow to cancel any entry wihtin that period
To allow entries again for given period you have to delete the accounting period that you have defined. To delete it go to accounting period and open it then from right top corner click menu and click delete.
Warning you will get if you try to pass any transaction between that period. Screenshot of warning shared below.