Why is there two of everything in Blocklab?

The 'Two of everything' you are referring to may be the Mobile and PC view.

We know how odd some text can look when it's larger on mobile, or how strange carousels can appear. With this in mind, we created an option to hide or view certain blocks for Mobile, PC and Tablet.

When in Blocklab, on the 'Block' tab, you will see these three icons:

The first icon is Mobile, second Tablet, and third PC/Laptop.

If you chose a block, for example an image block, and selected the Mobile icon, you will notice that on mobile this image block will not show. This can be done again for PC and Tablet; when deselected, these items will be hidden on said device. Have a try and see!