In Moodle, the "dock" is the upper-left corner of the screen. You can move one of the functional blocks to the dock ("dock the block") to make that block still available to you, while reducing the amount of space the block takes up on the screen:
When a block is "docked,", it appears as a tab in the left corner of your screen:
To see the full functionality of the block, you need to hover your mouse over the block to expand its content:
Occasionally, a student or faculty member will dock a block accidentally. To "undock" the block, click on the > icon that appears in the top-right corner of the expanded block:
The block will then return to its normal location on the right-hand side of the Moodle page.