When building keyboards, keys that are 2u or larger require a stabilizer. On a standard keyboard layout, this includes keys like the two Shift keys (2.25u and 2.75u), Enter (2.25u), Backspace (2u), and Spacebar (6.25u).
If you're not sure how many stabilizers you need, count up the number of keys on your keyboard layout that are 2u or larger. A 2u key is twice the length of a 1u key (i.e. the letters or numbers).
To learn more, read our Stabilizers 101 article →