Setting fields as required or mandatory in the initiation form using SharePoint designer

Todd Bleeker'sbook on WSS Development makes reference on page 471 (step 19) to a feature where SharePoint Designer can set certain fields in the initiation form as required. However, I do not see this option in the tool. Can anyone shed any light on this?
[415 byte] By [BartonFriedland] at [2008-2-19]

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