Viewing is by appointment only.

参观须预约。

《柯林斯英汉双解大词典》

Viewing of the house is by appointment only.

要看房只能提前预约。

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But free tours of other areas of the base are available -- by appointment only -- twice a month.

CNN: Where planes go to die

VIZIO's new 2013 HDTV collection will be on display at 2013 CES at the Wynn Hotel's Mouton Ballroom by appointment only.

ENGADGET: Vizio unveils 2013 HDTV lineup, upcoming XVT Ultra HDTVs promise 4K for the mainstream

Daniele Travi hosts wine tasting evenings by appointment only at Cantine Sorsasso (the Domasino Estate, Via Gaggio 1, Bis 22013, Domaso).

BBC: The spirit of the Italian Lakes