What arrows in Studio?
If you move a Part it will move based between where you ‘grabbed’ the item with the left mouse button and whatever Part surface is behind it.
So if you click on a Part with the left mouse button at the corner of the Part and drag it over a WedgePart it will align the first Part’s corner with whatever surface of the wedge is behind the mouse arrow you have on the Part.
Here’s a post about it from last year: Say hello to the new Lua dragger (Beta)