Definition
The point where a business cannot absorb more work no matter how much demand arrives. In service businesses it is rarely the crew or the equipment. It is usually the owner, because quoting, scheduling, follow-up, and customer questions all route through one person. Spending more on leads while the bottleneck sits there lengthens the backlog instead of raising revenue.
What it looks like in practice
A four-van appliance repair company doubles its ad budget in April and books almost no additional work. The vans are not the limit; the owner is. Every quote needs his number, every reschedule needs his call, and every unusual warranty question waits for him to get out of an attic. Leads arrive faster, sit longer, and a third of them go cold before anyone replies. In May he leaves the ad budget flat and hands off inbound response and estimate follow-up instead. Same demand, same vans, noticeably more booked jobs, because the queue finally drains at the speed the crews can actually work.
Why it matters
Owners usually diagnose a slow month as a demand problem, because demand is the thing marketing sells solutions for. The test is simple: if every new inquiry arrived tomorrow, could the business serve them without anything slipping? If the honest answer is no, more marketing buys a longer queue and a worse reputation. The uncomfortable part is that the constraint is often the owner personally, and that is not a discipline failure. It is what happens when a business grows on personal attention. The fix is to move whole responsibilities off that one person, not to work faster.