It is not the ornamental sword with which he is summoned, but rather the ability to utilize Excalibur with any tool he holds in his hands, based upon his habit in life of professing anything he held as being King Arthur's Excalibur. He can use it with the sword he wields or simply a mundane stick. He has been shown able to control how much energy is released, with his first attack destroying a large section of the Opera House that fell far short of his full strength, and using an even weaker attack to destroy a piece of debris to prevent it from injuring a police officer. When using the weaker attack, it did not seem to require the name of Excalibur being called, but merely unsheathing it. When utilizing the slash, it did not allude to the use of two hands for activation. The first use being shown was him unsheathing the blade with one hand as the other was on the scabbard. The second use was described as a motion reminiscent of a draw-slash from eastern swordplay.
It had been mentioned that its strength varies based on the item which is used to execute the Noble Phantasm, as seen when Saber was surprised by the amount of power that could be used with a tree branch, that then crumbled away after the usage. However, the strength will never reach the real Excalibur's, even if he were holding the real one.