Diagonal markers
One way to count rows of a pattern is by placing a stitch marker on a single stitch and counting up the number of loops between the marker and the needles. As you knit, the distance between them will grow at exactly 1 loop per row, indicating the total number of rows completed.
In contrast to a point marker which stays in one place, a marker can also be placed directly on the needle. Each time the marker is reached, it should be slipped up to the working needle. Slipping a marker will carry it vertically up the fabric on every new row, so I will call it a vertical marker. A vertical marker does not indicate the row count, however, because relative to the needles, the marker stays in one place.
A third type of marker, a diagonal marker, stays on the needle, like a vertical marker, but can be used for counting rows, like a point marker. As the name suggests, a diagonal marker traces a diagonal path along the fabric on each new row. Each time a diagonal marker is reached, it should travel one stitch horizontally while being transferred up to the next row on the working needle.
A diagonal marker has a 'rise' of 1 row and a 'run' of 1 stitch, giving it a slope of 1/1 = 1 row/st. If you place the marker in front of the first stitch on the left needle before working a row, after completing one row the marker will shift one stitch to the left. After two rows it will be shifted two stitches to the left and so on for future rows. This makes diagonal markers an excellent tool for counting rows, as you can simply count the number of stitches to the right of the marker.
Diagonal markers remind me of swimming laps in a pool. The discs on a lane divider in a swimming pool look a lot like the stitches on a needle. In order to keep count of the number of laps, swimmers often slide a single disc each time they reach the end of the pool.
The practice of diagonal markers is most likely not original, but I couldn't find much in terms of directions or specific mentions of it or similar terms. Reddit is the only source I could find of a similar concept. I'd like to make the process explicit in order help knitters keep track of rows easier.
However, some patterns are ill-suited for diagonal markers. Diagonal markers have undefined behavior if they pass through a cable or lace pattern, for example. In those cases it may be possible to find a section of the pattern marked by two vertical markers that the diagonal marker can move between.
Construction
A diagonal marker should travel a single direction relative to the fabric, typically from the right to the left. For knitting in the round, that means passing the marker in the same direction each time you reach it, however for flat items the direction should be flipped on the wrong side.
Because the marker stays on the needle, it is not necessary for it to be able to clip off like a typical stitch marker. Any type of closed loop, like an old key chain loop, will do.
Pass Marker to the Left
For knitting or purling, work until you reach the marker. Work the following stitch without sliding it off the left needle then insert the working needle into the marker as if to knit. Pull both the stitch and the marker off of the left needle.
Pass Marker to the Right
Work until one stitch before the marker.
Knit
Insert the needle as if to knit two together the marker and the first stitch. Wrap yarn around the working needle and pull it through only the first stitch. Slide both the stitch and the marker off the left needle.
Purl
Insert the needle as if to knit two together the marker and the first stitch. Slip both the stitch and the marker to the right needle. Insert the left needle into the front of only the first stitch from right to left, as if to knit with the wrong needle. Slide the stitch back to the left needle then purl as normal.
Advanced Use
One is not the only possible value for the slope of a diagonal marker.
Two diagonal markers with differing slopes can be used to create a two digit numbering system for a project. Consider a flat piece with sixteen stitches per row. If you place a single marker (m) on the left needle and pass it one stitch to the left every row, you can count up to sixteen rows before the marker falls off the needles and you'll have to start over the count.
----------------m < beg. of row 1 > ---------------m- row 2 --------------m-- < row 3 ... --m-------------- < row 15 > -m--------------- row 16 (m falls off) ----------------m < row 17
Before doing so, on the 17th row, you could place another marker (M) on the left needle and the first marker (m) to the right of it.
----------------Mm < beg. of row 17
Treat both markers as one diagonal one on this row: work the first actual stitch and then insert the right needle as if to knit both markers. On future rows, m will be passed one stitch to the left while M will be slipped as if it was a vertical marker.
> ---------------mM- beg. of row 18 --------------m-M- < row 19 > -------------m--M- row 20 ------------m---M- < row 21 ... --m-------------M- < row 31 > -m--------------M- row 32 (m falls off) ---------------M-m < row 33
After sixteen more rows, m will fall off the needles again and need to be placed on the left needle at the start of the 33rd row. After one more row, m should be directly to the right of M again. Each time m meets M, you should treat them as one for the next row and shift them both to the left one stitch as described above.
> ---------------Mm- beg. of row 34 --------------mM-- < row 35 > -------------m-M-- row 36 ------------m--M-- < row 37 ...
Because there are sixteen stitches per row, each marker now represents a digit in a base-16 numbering system. In order to convert to the decimal system to figure out how many rows have been completed, you can follow this formula:
(16 x CM) + Cm
Where CM is the count of stitches to the right of the marker M, including the other marker m, and Cm is the count of stitches to the right of the marker m, without including M.
For a different example, consider a project that looks like this:
-----------M----m-----
There are twenty stitches total, CM = 10, Cm = 5. That means that (20x10)+5 = 205 rows have been completed and so you are on the 206th row.
Here is another example using two more vertical markers (|) to mark off a section of a pattern.
---|----m----M--|---
Ten stitches are marked off, so with CM = 2 and Cm = 6, the number of rows completed is 26.
Generally speaking, this method allows you to count up to S2 - 1 rows, where S is the number of stitches per row or the number of stitches marked off.
Conclusion
I hope this guide provides you with a different way to think about keeping track of rows that does not require much in terms of special equipment. One of my favorite parts of this method is that, most of the time, it doesn't require you to stop knitting in between rows to make a mark on a piece of paper or digital row counter. The act of counting becomes part of the knitting process itself.
All three types of markers, vertical, diagonal, and even point markers, can be powerful tools for a knitter. Add them to your knitting arsenal to tackle any long project.