Worst-case scenario: the UEd Goblin wipes the map and burns down your house.
From Unreal Wiki, The Unreal Engine Documentation Site
Something about the grid in UEd.
Things to cover include:
- How to set grid size.
- Why it's best to keep brushes on the grid. See, the Snap to Grid Feature.
- How to make other actors snap to grid
- mention that snap to point seems buggy
Advanced Grid Options
These are set under UnrealEd Advanced Options.