Probably your client needs a basic explanation on why necking is used.

• Necking is needed to visually illustrate when the segments do not represent the end of the activity as well as when no work is scheduled or was performed. Necking is not only the result of non-work periods but can also be the result of resource leveling when splitting of the activity is allowed. Necking is good to visually disclose different shift assignments and make sure shift model works as expected. Necking can also be the result of actual progress interruptions as well as as when out-of-sequence occurs. I personally find it also a necessity when in progress work is interrupted as to stop the activity clock or calculation of its work duration. It is good practice to show a bar for planned work as well as a neck. Seasoned schedulers find it a necessity. Hiding the neck would be bad scheduling practice.
• In the following figure you will notice Bricks installation on A begins at second shift because delivery happened during first shift after materials scheduled for this building were depleted.
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• If you expand the timescale you can see how we have an 8 hr shift and a second shift hour shift without need to look at the calendar details. Visual aids help to understand the schedule.
• Perhaps when necking is due to resource leveling it should be in another color [perhaps Yellow] and when due to out-of-sequence scheduling in another color [perhaps Black].

Is there any way of blanking out the non work time so it only shows when work is being done? I've a client who can't get their head around the idea of the necked bars.

thanks