Adjacent-Finger Roll Drill (as sd re io)
as sd df jk kl re io er oi
Every passage contains: as sd df jk kl re io er oi
QWERTY layout assumed. Backspace corrects; uncorrected errors count against net WPM.
"as", "sd", "df", "jk", "kl", "re", "io", "er", and "oi" all share one property the same-finger drill's pairs don't: each letter is typed by a different finger, and those two fingers sit right next to each other on the same hand. That neighbouring arrangement is what makes a roll possible — the second finger can start moving down while the first is still coming up, so the two presses overlap in time instead of queuing one after the other.
That overlap is why rolls are generally reckoned to be the fastest sequences a hand can produce: nothing about them requires waiting. "as", "sd", and "df" walk the left hand's home row from the pinky toward the index finger; "jk" and "kl" walk the right hand's home row the other way, from the index finger out toward the ring finger. "re" and "io" repeat that outward direction one row up, while "er" and "oi" are the exact same two keys run in reverse — the only thing that changes is which finger goes first.
Why This Drill
The general finding on rolls is that the inward direction — moving from the little finger toward the index finger — comes out faster than the same two keys run outward. "er" and "oi" are the inward versions of "re" and "io"; typing all four back to back is a direct way to feel that difference on identical keys rather than take it on faith.
Practising this drill sharpens the timing of the overlap itself: how early the second finger can safely start moving without landing before the first key has actually registered. Too cautious, and you lose the speed advantage a roll is supposed to give you; too early, and the second letter can arrive before the first, which shows up as the two characters swapped rather than in their intended order — exactly the kind of transposition the Speed Building: Common Letter Pairs lesson first introduces at a gentler pace.
Because this is the fastest category of bigram, it's also the most useful one to compare against a slower class like the Same-Finger Bigram Drill — a wide gap between the two numbers is a rough measure of how much of your ordinary typing still runs below its physical ceiling, held back by pairs that never get any overlap to work with.
Why Neighbouring Fingers Can Overlap and a Shared One Can't
Two adjacent fingers are separate, independent parts of the hand, so one can be descending toward its key while the other is still lifting off its own — the two motions happen on different fingers at the same time. A single finger asked to hit two keys, the situation the Same-Finger Bigram Drill isolates, has no such option, because there's only one finger available to do both jobs in sequence. The distance between the two keys barely matters next to this difference; a same-finger pair one row apart is still slower than an adjacent-finger pair one row apart, because only one of the two ever gets to overlap.
Reading the Direction: "re" Against "er"
"re" sends the index finger down first and the middle finger second, moving away from the index finger's own position — an outward roll. "er" is the identical two keys with the order flipped, so the middle finger leads and the index finger follows toward it — an inward roll. "io" and "oi" repeat exactly the same contrast one hand over. If one direction in each pair consistently comes out quicker for you, that's the general inward advantage showing up in your own typing rather than a coincidence of these four particular keys.
What the Left-Hand and Right-Hand Sets Are Each Testing
"as", "sd", and "df" cover three consecutive steps of the same inward sweep on the left hand, so typing them in order is close to typing the whole home row's inward motion in one pass. "jk" and "kl" do the outward version on the right hand's home row. Because the two hands don't share fingers, there's no reason to expect identical speed on the left-hand and right-hand sets — a real gap between them says something about which hand's finger independence needs more work, which is a different question from the Row-Jump Bigram Drill's concern with vertical distance rather than which fingers are involved.
Frequently Asked Questions
What actually makes two fingers count as 'adjacent' here?
Fingers that sit physically next to each other on the same hand — index and middle, middle and ring, or ring and pinky — rather than fingers that are two or more positions apart, like index and pinky, which don't overlap in the same clean way.
Why do "re" and "er" use the exact same two letters?
So direction is the only variable. Every other pair in this drill uses a different letter combination, but "re"/"er" and "io"/"oi" hold the keys constant and flip only the order — the cleanest way to feel whether inward or outward comes out faster for you.
Is a roll always faster than typing the same two letters with no overlap available?
Within this drill, yes, since the whole set is chosen to overlap. The comparison worth making is against the Same-Finger Bigram Drill, where no overlap is available at all, regardless of direction.
Why does the drill split between the left hand's home row and the right hand's?
So you can compare your inward sweep on one hand against your outward sweep on the other without switching hands mid-comparison — "as", "sd", "df" stay entirely on the left, "jk", "kl" stay entirely on the right.
Should typing these feel almost effortless once I know the pattern?
Close to it, eventually — rolls are the category of bigram with the least structural resistance, so once the timing of the overlap is comfortable, these pairs should sit near the top of your speed range rather than the middle of it.
Does this drill help with hand-alternation typing too?
Indirectly — both rely on independent parts of the body moving without waiting on each other, but the Hand-Alternation Bigram Drill covers the cross-hand version specifically, where the two moving parts aren't neighbouring fingers on one hand but the two hands themselves.