Eleven years ago, stuck aboard a bouncing little commuter jet, circling Boston in a gusty snowstorm that would not let up, I found myself cursing my fancy job as a consultant, my hard-driving boss, and my crazy, unmanageable life. Plus I was sobbing. My daughter's Christmas play started in 15 minutes and I had promised I absolutely, positively would not miss it. I missed it.

A few months later, I quit. I had found a publishing company where my new boss told me I could not only travel less, I could work at home two days a week. When I started, I discovered dozens of colleagues like me, holding it together at home and on the job thanks to flextime. Almost every kind of arrangement seemed okay with our boss—as long as we delivered results.

Filled with relief and gratitude, we did. For many of us, flextime made both a healthy family situation and a meaningful work experience possible at once. It was a lifesaver.

That's why, when I was promoted a few years later, I was determined to follow my boss's example. With my help, I vowed, parents would find that elusive balance between kids and work; adult children would be able to care for their elderly relatives with less stress. And everyone would be happy.

Except, in pretty short order, I wasn't. Within weeks the flextime I had so loved as an employee had become a throbbing headache for me as a boss—with its tangled-up logistics, lowered productivity, and contentious employee relationships. (Who knew non-flextime users could resent their flextime colleagues so bitterly?)

Still, I kept my mouth shut. I knew flextime had to exist or I'd lose good people. I also didn't want to sound like the hypocrite I'd become. But most of all, I was silent because I thought I was alone in my struggle. I wasn't—not by a mile.

Over the past four years, my husband, Jack, and I have spoken with thousands of bosses caught in that same bind. They get the virtues of nontraditional scheduling but grapple with its implementation. Recently, we codified our research, and the result is a four-point list of tacit truths about flextime—from the boss's point of view.

Bosses wish employees understood that their priority is competitiveness.

Bosses have hearts and consciences, but not at the expense of the company's success. Flextime makes profitability harder. On the revenue front, for instance, flextime employees are simply in the office less (if they're telecommuting) or can't always be reached (even if they're working four ten-hour days). Not good—not good for the customer, and not for the boss who gets called instead and suddenly has a piece of work on his plate that he knows isn't really his.

On the expense front, there is no pretty way around the fact that flextime decreases output. Employees who are "working at home" are not always working (more about this later). The bosses we spoke with estimated that when employees go from traditional full-time to flextime, they lose about 20 percent of their productivity. Ouch.

Secondly, bosses wish employees understood exactly what flextime is. Some employees strike part-time arrangements with their companies and are paid accordingly. Flextime is different.

Technically, flextime is full-time work, or close to it, but with an elastic, negotiated schedule. Still, some employees persist in seeing flextime as if it were a part-time deal in terms of hours or, worse, from a boss's point of view, as a defined benefit, like the company dental plan.

Your boss sees flextime as an old-fashioned chit system in which the more you deliver, the more freedom you earn. To be blunt—no matter what the official company policy, bosses see flextime as a reward for outstanding performance. They don't particularly like giving it to average players, and they loathe giving it to the barely-hanging-in-theres.