Field help (TASPRL) 

This check box is selected automatically if the All tasks check box (field TACALL) is selected. Leave this check box selected to copy all material requirements tasks from the source project to the destination project. If you do not want to copy material requirements tasks to the destination project, clear this check box.

 With this check box selected, all material requirement task lines in the operational (task) structure are selected. You can, however, deselect lines that are not to be copied by clearing individual check boxes (in the Tasks section).