12. Explain what plan you would use to inform the packer of the description of the goods to be shipped, but prevent him from knowing the quantities, in order to further prevent him from double-checking the figures showing quantities and at the same time neglecting to count the articles. 13. Where the firm sells three or four classes of goods and wishes to keep a continuous record of the tonnage sold, that is, weight of the various classes of goods, how would you rule the invoice and sales sheet in order to shorten the billing? 14. If you were forced to substitute one size of an article in place of another size ordered (without injury to the customer), how would you design your forms in order to enable you to typewrite the size shipped and size ordered on the sales sheet, and size ordered, only, on the invoice? 15. If you wish to typewrite a requisition for goods ordered at the time the invoice and sales sheet are written, how would you arrange it? 16. What is the difference between the terms _unit billing_ and _condensed billing_? Under what conditions would you recommend unit billing and when condensed billing? 17. What is the best plan of facilitating the filling of orders where there are a large number of floors or departments and where each day's orders are supposed to be filled upon the day the orders are received? 18. Why should a plan which is highly satisfactory in a small concern prove to be an absolute failure in a large one? 19. What is meant by _split orders_? 20. Describe the different forms of punched holes of loose-leaf sheets and why the closed-hole punching is not adapted for use with records which are to be removed and replaced in binders from time to time. 21. Describe the different forms of binders with which you are familiar. 22. In printing invoices what is the best plan of designing the headings in order to facilitate the execution of the invoice on billing machines? Would you pay any attention to the space between the lines of the heading and to the distance between the last line to be typewritten on the heading and the first line to be typewritten on the invoice? 23. Explain the mistakes made in using carbon paper, and under what conditions you would use the various weights of carbon paper. 24. Explain what is meant by a _blind_. 25. Explain what is meant by _credit memoranda_, and tell how to use them in connection with a sales book instead of having to use a separate credit sheet. 26. Explain the use of special characters on the billing machine, and what is meant by aligning them in order to prevent one abbreviation being printed over the top of another. 27. Explain the difference between a single-stop tabulator and a decimal-stop tabulator. 28. What is the advantage of having a billing operator on a platform on wheels in a wholesale dry goods house? 29. Under what conditions would you recommend the use of the separate billing machine and separate computing machine for the same work?