Trims objects to meet the edges of other objects.
To trim objects, select the boundaries. Then press Enter and select the objects that you want to trim. To use all objects as boundaries, press Enter at the first Select Objects prompt.
"The TRIM command allows you to shorten an entity to an intersection or remove a section of an entity between two intersections."
PS ... Are you seriously asking this question on a "specialists" forum?
In the command prompt type TR then select boundaries from where you want to trim,, Then Enter/Space Bar and click the object you want to trim.. And another short cut for this is type TR then hold shift and click the object you want to trim..
