Trapdoor shortcuts are shortcuts made by accessing a trapdoor which leads to a different location. Trapdoors can be upgraded to shortcuts as rewards for completing minigames and quests.
Grand Exchange to Keldagrim[]

Trapdoor leading from Grand Exchange to Keldagrim
There is a trapdoor located in the north-western corner of the Grand Exchange, near the shortcut tunnel, which leads to the dwarven city of Keldagrim. The message when opening the Grand Exchange trapdoor says: This trapdoor leads to a small dwarven mine cart station. The mine cart will take you to Keldagrim.
Canifis to Mort'ton[]

A trapdoor shortcut in Canifis to Mort'ton
There is a trapdoor located behind the Hair of the Dog tavern in Canifis which can be upgraded to a trapdoor shortcut to Mort'ton, placing the player near Cyreg Paddlehorn, by completing Temple Trekking. It is a reward for training Zachory Bragg to level 99, and can be activated or deactivated by using the Temple Trekking signpost near Paterdomus.