locktable codeunit 74

Can somebody explain why Navision uses LOCKTABLE when you get receiptlines in your purchase. The code used in Navision 2.60 in codeunit 74 Purch.-Get Receipt is: Purchline.LOCKTABLE; (NL:InkRegel.LOCKTABLE;) Purchheader.LOCKTABLE; (NL:InkKop.LOCKTABLE;) In Navision 3.60 the LOCKTABLE on the purchheader disappeared but I wonder why the LOCKTABLE on the purchline is still there and what the function is.

This function is used to lock table and protect from write transactions by other users and the other possible use is to make sure that no other user makes changes between the read and the possible write.