A library catalogue card is of a standard size 12.5cm * 7.5cm.It may be a white blank card or a card with lines printed on it. See the illustrations given below for the two types or cards:
The indention lines are drawn mainly to maintain clarity and to distinguish one line from another line while recording the details of a document in the form of a catalogue entry. For the convenience of user the details of a document are recorded in different paragraphs. Each paragraph starts from second indention (i.e., second red line) and continues from first indention (i.e., first red line) in the description. However, in the case of the Main line the starting indentions for heading differ between main and added entries. The heading section/leading section both in dictionary and classified catalogue starts from first indention (First red line). But heading continues from second indention in dictionary catalogue and from first indention again in classified catalogue.
One important factor we must always remember here is that the code which we are following for preparing dictionary catalogue, i.e., AACR-2R never prescribes any indentions in the form of rules in the code except a suggestion for providing heading or access point distinctively in a separate line from the description of a document in the catalogue record/entry. On the other hand CCC offers clear and rigid rules for following different indentions for different sections in different entries.