The Clipboard is a simple way to copy existing Blocks and paste them around a site
Adding a block to your Clipboard
Put your page in Edit mode, click on the block you would like to copy to your clipboard, click Copy to Clipboard.
Placing a Block from the Clipboard
Put the page in edit mode. Open the block add pane by clicking the plus sign on the top bar. Click the downard arrow next to the word "Blocks" and select "Clipboard".
This brings up a list of all your clipboard items for you to pick from. You will see a preview of the block below its name ("Form" in the screenshot below). You can also delete any of them by clicking "Delete" next to the block name:
To add them to the page, you can drag these blocks out of the panel into an area just like any block. Dragging should start by clicking on the block's name.