Zero All Clearances
Zero (and Restore) all clearances is a feature of several RCT trainers. It was first introduced by the beast trainer in 2002. All static objects on the game map have a base height (the height of the bottom of the object) and a clearance height (the top of the object). If the clearance height is set to zero then it is possible to intersect that object when placing scenery, track pieces etc. The ‘Zero All Clearances’ option sets the clearance height of everything on the map to 0.
Objects without the correct clearance height will not be displayed correctly, so once you are finished you need to use the Restore All Clearances option to reset the clearance height of every object on the game map.
The Beast, 8Cars and 4Cars all have the Zero All Clearances and Restore All Clearances functions as first seen in the Beast Trainer. Codex has a slightly different feature and the map control can usually be used to achieve the same result with more precision.
Son Of Beast and the Save Game Modifier both have a Zero All Clearances option but no Restore.