To work with 3D files, enable the Consider Z option in the Preferences dialog. This setting allows line cleaning tools to utilize Z values. When not checked, all Z values are considered equal.

When enabled, element Z values will participate in calculations in the following tools:

• Find Duplicate Linework
• Find Similar Linework
• Find Linework Fragments
• Thin Linear Element
• Segment Linear Element
• Find Gaps
• Find Dangles
• Connect Linework
• Find Slivers
• Validate Topology
• Create Centroids
• Create Shapes