The icon for Match Frame is the same one used for Master Clips. By default, the Match Frame function can be found under the Source Window as well as in the Fast Menu Tool Palette in the Timeline Toolbar.
The most common mistake I see made is when people want to use Match Frame to match back from the Timeline window (as we will be doing in the example recipe in a moment) they mistakenly click on the Match Frame button that's under the Source Window. Instead, to Match Frame from the Timeline window, either use the Match Frame button found in the Fast Menu Tool Palette or you can map it to a convenient location under the Record Monitor, on the Timeline Toolbar, or on your keyboard.
See the Mapping buttons and menu selections recipe in Chapter 2, Customizing Your Work Environment for more information if you are unfamiliar with mapping.