everquest

How to fix the gaps at the edge of each ADT? I tried using the Hole tool to cut off the mountain-like margins and when I tried to fill the leftover gaps, either with Hole tool (shift+click) or Fill all gaps (Assist menu), they appear again. These are the gaps i'm talking about (after deletion). Is there a way to fix them? I followed the guide on the Tutorials sections. For clarifying, these are the "mountain-like" margins that were at the edge of each ADT once I created the map.