Trim & Extend

Trim

Remove partial of the object based on cutting edge

Thaw Column layer

Home tab > Modify panel > Trim

Select 2 columns as cutting edges
Press [Enter]

Select lines inside columns and intersect with columns

Select lines inside the other columns
Press [Enter] to end the command

Home tab > Modify panel > Trim

Select 2 columns as cutting edges
Press [Enter]

Cross-select lines inside the column

Cross-select lines inside another column

Press [Enter] to end trim command

Extend

Extends objects to meet the edges of other objects

Home tab > Modify panel > Extend

Select the line as boundary edge
Press [Enter] to end the boundary edge selection

Hover over the line to preview
Select the line

Hover over the bottom line to preview

Select the bottom line