We’ve posed that question to managers, engineers, salespeople, and consultants in companies around the world. The response we get is almost always the same: vertical relationships.

But when we ask, “Which relationships are most important for creating value for customers?” the answers flip. Today the vast majority of innovation and business-development opportunities lie in the interfaces between functions, offices, or organizations. In short, the integrated solutions that most customers want—but companies wrestle with developing—require horizontal collaboration.

The value of horizontal teamwork is widely recognized. Employees who can reach outside their silos to find colleagues with complementary expertise learn more, sell more, and gain skills faster. Harvard’s Heidi Gardner has found that firms with more cross-boundary collaboration achieve greater customer loyalty and higher margins. As innovation hinges more and more on interdisciplinary cooperation, digitalization transforms business at a breakneck pace, and globalization increasingly requires people to work across national borders, the demand for executives who can lead projects at interfaces keeps rising.

Our research and consulting work with hundreds of executives and managers in dozens of organizations confirms both the need for and the challenge of horizontal collaboration. “There’s no doubt. We should focus on big projects that call for integration across practices,” a partner in a global accounting firm told us. “That’s where our greatest distinctive value is developed. But most of us confine ourselves to the smaller projects that we can handle within our practice areas. It’s frustrating.” A senior partner in a leading consulting firm put it slightly differently: “You know you should swim farther to catch a bigger fish, but it is a lot easier to swim in your own pond and catch a bunch of small fish.”

One way to break down silos is to redesign the formal organizational structure. But that approach has limits: It’s costly, confusing, and slow. Worse, every new structure solves some problems but creates others. That’s why we’ve focused on identifying activities that facilitate boundary crossing. We’ve found that people can be trained to see and connect with pools of expertise throughout their organizations and to work better with colleagues who think very differently from them. The core challenges of operating effectively at interfaces are simple: learning about people on the other side and relating to them. But simple does not mean easy; human beings have always struggled to understand and relate to those who are different.

Leaders need to help people develop the capacity to overcome these challenges on both individual and organizational levels. That means providing training in and support for four practices that enable effective interface work.

[Here is the first practice.]

1. Develop and Deploy Cultural Brokers

Fortunately, in most companies there are people who already excel at interface collaboration. They usually have experiences and relationships that span multiple sectors, functions, or domains and informally serve as links between them. We call these people cultural brokers. In studies involving more than 2,000 global teams, one of us—Sujin—found that diverse teams containing a cultural broker significantly outperformed diverse teams without one. (See “The Most Creative Teams Have a Specific Type of Cultural Diversity,” HBR.org, July 24, 2018.) Companies should identify these individuals and help them increase their impact.

Cultural brokers promote cross-boundary work in one of two ways: by acting as a bridge or as an adhesive.

A bridge offers himself as a go-between, allowing people in different functions or geographies to collaborate with minimal disruption to their day-to-day routine. Bridges are most effective when they have considerable knowledge of both sides and can figure out what each one needs. This is why the champagne and spirits distributor Moët Hennessy España hired two enologists, or wine experts, to help coordinate the work of its marketing and sales groups, which had a history of miscommunication and conflict. The enologists could relate to both groups equally: They could speak to marketers about the emotional content (the ephemeral “bouquet”) of brands, while also providing pragmatic salespeople with details on the distinctive features of products they needed to win over retailers.

Understanding both worlds, the enologists were able to communicate the rationale for each group’s modus operandi to the other, allowing marketing and sales to work more synergistically even without directly interacting. This kind of cultural brokerage is efficient because it lets disparate parties work around differences without investing in learning the other side’s perspective or changing how they work. It’s especially valuable for one-off collaborations or when the company is under intense time pressure to deliver results.

Adhesives, in contrast, bring people together and help build mutual understanding and lasting relationships. Take one manager we spoke with at National Instruments, a global producer of automated test equipment. He frequently connects colleagues from different regions and functions. “I think of it as building up the relationships between them,” he told us. “If a colleague needs to work with someone in another office or function, I would tell them, ‘OK, here’s the person to call.’ Then I’d take the time to sit down and say, ‘Well, let me tell you a little bit about how these guys work.’” Adhesives facilitate collaboration by vouching for people and helping them decipher one another’s language. Unlike bridges, adhesives develop others’ capacity to work across a boundary in the future without their assistance.

In addition, leaders can develop more brokers by giving people at all levels the chance to move into roles that expose them to multiple parts of the company. This, by the way, is good training for general managers and is what many rotational leadership-development programs aim to accomplish. Claudine Wolfe, the head of talent and development at the global insurer Chubb, maintains that the company’s capacity to serve customers around the world rests on giving top performers opportunities to work in different geographies and cultivate an international mindset. “We give people their critical development experiences steeped in the job, in the region,” she says. “They get coaching in the cultural norms and the language, but then they live it and internalize it. They go to the local bodega, take notice of the products on the shelves, have conversations with the merchant, and learn what it really means to live in that environment.”

Matrix organizational structures, in which people report to two (or more) groups, can also help develop cultural brokers. Despite their inherent challenges (they can be infuriatingly hard to navigate without strong leadership and accountability), matrices get people used to operating at interfaces.

We’re not saying that everyone in your organization needs to be a full-fledged cultural broker. But consciously expanding the ranks of brokers and deploying them to grease the wheels of collaboration can go a long way.