You may need to delegate some approver rights to other placement when approvers are not at the office(on holiday/business trip)
1) Go to Staff --> Placement Delegation --> Add New
2) Input Start Date and End Date for the effective period of this role
3) After the effective period is over, this placement is no longer able to perform such rights anymore.
If you want to do it in ESS, you can take a look the following page.