上屋抽梯
Stratagems of Combining · 并战计Lure the enemy into a trap, then cut off their retreat. Give them a way in but no way out.
Liu Bei asked to borrow Jingzhou from Sun Quan, promising to return it later. Once he had it and fortified his position, there was no practical way for Sun Quan to reclaim it — the "ladder" of negotiation had been pulled away.
Games like Candy Crush offer free entry (the ladder up), then make progression impossible without purchases once players are invested (the ladder removed). The initial generosity creates dependency that enables later monetization.
Enterprise software companies offer steep initial discounts and easy onboarding (the ladder). Once the customer's data and workflows are embedded, switching costs become prohibitive (the ladder is removed). The customer is now on the roof with no way down.