How to Check All Boxes in Airtable at Once
Airtable does not have a "select all and check" button for checkbox fields. Clicking the column header selects the column but does not toggle the checkboxes. This trips people up when they want to mark a batch of records as done, approved, or complete in one action.
There are two practical ways to do it.
Copy-paste method

This is the fastest approach for a one-off task, and it's especially useful after filtering a view, when you only want to check the records currently shown rather than every record in the table.
Click on any checkbox that is already checked in the column. Copy it with Cmd+C (Mac) or Ctrl+C (Windows).
Select the checkbox cells you want to update by dragging through the range, or click the top cell and Shift-click the bottom cell to select everything in between. You can also use the fill handle, the small square in the corner of a selected cell, and drag it down through the column to copy that cell's value into every row you drag across.
Paste with Cmd+V or Ctrl+V. Airtable fills every selected cell with the checked value.
To uncheck all, do the same thing but copy an unchecked cell first.
Automation method
For a repeatable workflow, set up a simple automation.
For a manual, on-demand version, use the "When a button is clicked" trigger. You might expect this to connect to a Button field on the table, since that's the more familiar place to put a button, but table Button fields don't have a "Run automation" action to offer.
Their options are things like Open URL, Open in Page Designer, and Run script. Only a button inside an Airtable Interface has "Run automation" as an available action, which is why this trigger needs an Interface rather than a table field.
Open or create an Interface, add a button (either as a standalone button element or on a record detail layout), and set its action to Run automation. Point it at the automation you're building, then finish configuring the automation's steps and turn it on. Publish the Interface, and the button is live: click it, and the update runs.
The action is a "Find records" step to find the records you want to update, followed by a repeating group that runs an "Update record" action on each one, setting the checkbox field to checked. Keep in mind Find records can return up to 1,000 records per automation run, so on a very large table you may need a filtered view or additional conditions to make sure the records you care about are included.
If you want to reset checkboxes on a schedule instead, for example unchecking a weekly task list every Monday, you don't need a button at all. Use the "At a scheduled time" trigger instead, running weekly, with the same Find records → repeating group → Update record structure, setting the checkbox field to unchecked. "Reset" here means unchecking, which is a separate automation from the one above that checks boxes.