By default users will have no permissions to view or set a block in the calendar.
Setting permissions per user
Users need to have permissions to set a Calendar Block.
To allow users to set or view a block in the calendar, click on "Settings"
Next click on "User Management"
Click on the lock button to change permissions for the user.
Now you will see all the user permissions. You will find the "Calendar Block(s)" permissions here.
You have the following options to set the permissions:
None, the user will not see Blocks
View, the user can see the block, but can not edit the block
Manage, the user can see and edit the block, but can not delete the block
Administrate, the user can see, edit and delete the block
This way you can manage who can view, edit or delete the Calendar Block functionality.