1.   And to avoid the controversy, consider installing an electric fence, an invisible boundary that will keep the dogs in and other critters out.

2.   Hands push at invisible boundaries, embrace and shove others away and signal power, sometimes comically.

3.   In all the traditional tales the fox keeps its distance, a playful distance perhaps, always respecting the invisible boundary between wildness and not-wildness.

4.   Section lines refer to the invisible boundaries that divide the state vertically and horizontally into segments of one square mile each.

5.   The landscape unfolded dramatically as we moved downriver and crossed the invisible boundary between the Yukon Territories and British Columbia.

6.   The importance of the Dry Tortugas as a spawning grounds extends far beyond its invisible boundaries.

7.   They can be adjusted to set off remote alarms, audible or silent, when patients cross invisible boundaries set by their attendants.

8.   Turf-conscious animosity is palpable inside, as rival priests and monks keep an eye on the invisible boundary lines that separate their properties.

9.   It abuts the so-called Green Line, the invisible boundary between Israel and the West Bank.