Altaïr has the ability to grasp in the prologue, however, he is stripped of it and becomes again a novice in the Creed. Later, in Memory Block 4, he receives a promotion to a higher rank, with it the gloves (equipment that allows him to grasp).

The ability to grasp is very useful if you want to reach very far places. It will be necessary when taking one of Richard's Flags in the Kingdom. You position yourself on a pillar as in the picture:



Then while in the air you press the red key for action GRASP, which by default is SHIFT on PC:



You should successfully land with your hands grabbing the ledge.



If you still cannot land on it, try switching on V-SYNC and/or setting a lower screen resolution.