You can create a contoured availability that contains several different unit values over time. Closed-end availability is when the first row is a date in the Available From field and/or the last row is a date in the Available To field. This specifies that prior to the date in the first row's Available From date and after the date in the last row's Available To date, the resource is not available (the Max Units value is 0%).
Double-click on the resource you want to define.
If the first row's Available From date contains a date, the resource will have a Max Units value of 0% any time prior to that date, making it unavailable for work on the project. If this field contains the value NA, the resource is available for the Units value on this row up until the Available To date.
Make sure that there are no breaks between the Available To date on one row and the Available From date on the next row. If a break occurs, the resource will not be available (0%) during the time between the dates.
If the last row's Available To date contains a date value, the resource will not be available (0%) for any dates after this date. If you want the resource to be available at the Units value on this row for all dates after the Available From date, type NA in the Available To date field.
This example has the resource available at 0% for all dates prior to 7/1/2004. It then has him available at 25% from 7/1/2004 to 7/30/2004. Between 7/31/2004 and 8/31/2004, he is available at 50%. Then between 9/1/2004 and 9/30/2004, he is available at 100%. Finally, after 9/30/2004, he is available at 0%.