Filet crochet is lace that draws: a grid of squares, where a filled square is a block and an open square is a space. The blocks carry the design — hearts, words, lattice — and the spaces are the background the design sits on. The whole craft runs on crochet thread and just two stitches, the chain and the double crochet, worked from a chart that reads like the other grid crafts' charts in this family.
It is the quietest of the grid crafts about color: filet is worked in one thread, and the picture comes from the holes, not the palette. Every filet draft in the drafts gallery is a single color. That's also what makes old filet patterns so reusable — the same block-and-space chart works in size 10 thread for a table runner and a whole size bigger for a curtain panel, and the picture never changes.
The grid is small but literal. One chart square is one mesh square, and at the size-10 gauge the engine starts with — about 4 squares to the inch — a 33-square-wide panel like the gallery's HOME panel is about 8¼ in across. The chart is the pattern and the pattern is the chart; nothing scales between them but your hook.
Here is the mechanic everything else stands on: a block is three double crochet — the upright post at its edge and two posts filling it — and a space is chain 2 and one double crochet for the post, which leaves the square open with a chain running along its top. Squares side by side share their posts: the third stitch of one square is the next square's edge post. That's why a row of squares has one more post than it has squares — filet's counting rule ("3 per square, plus one"), and the reason the pictures stay square-ish while the rows stay countable.
Because each square sits either on a block or on a space, there are exactly four ways a square can be worked, and every filet pattern is those four sentences in different combinations:
| Working | The sentence |
|---|---|
| Block over a block | A double crochet in each of the next 3 stitches |
| Block over a space | 2 double crochet in the chain-2 space (or one in each of its 2 chains), then 1 in the next post |
| Space over a block | Chain 2, skip 2, double crochet in the next post |
| Space over a space | Chain 2, double crochet in the next post |
Every block and space ends on a post — so a missed stitch shows up as a missing post rather than hiding in the hole pattern. Counting posts as you work each row is the early-warning system: N squares want N+1 posts. And the row starts the same way every time: chain 3 at the start of a row stands for the first post, even when the row opens with a space — then chain 2 more for that space. Some patterns write those same stitches as one "chain 5" at the turn; the app spells them out instead, so you always know what each chain is doing.
One naming trap before you buy a pattern: US and UK patterns name stitches differently — a US double crochet is a UK treble. This guide and the app both use US names.
The foundation chain is the one piece of arithmetic the craft asks for, and it's a formula: chain 3 for every square, then 3 more if row 1 starts with a block, or 5 if it starts with a space. The extra chains stand for the first post — 3 — plus, on a space start, the top of that first space — 2 more: row 1 then begins with a double crochet in the 8th chain from the hook, which finishes the first space and leaves one space fewer to work in the row. The app's Make tab prints the exact count for whatever chart you've drawn.
Two published checks that the formula matches practice: Red Heart's filet pattern RHC0518 chains 180 for 59 blocks — exactly 3 × 59 + 3 — and Crochet Cabana's filet pages chain 24 or 26 for 7 squares, matching the block and space starts. One caution that took the engine a revision to get right (fixed in the app's October 2026 review): the "plus 1" some tutorials list after "3 per square" is the row's last stitch you'll work into, not an extra chain — the app now says so.
The app reads the rows the way you'll work them — a row reads like 14 blocks, 1 space, 6 blocks, and each of its runs also says what it sits over, so the chain-2 vs 3-dc choice is spelled out per run. Between rows the app's own checklist is the same three habits: right side facing, chain 3 for the first post, last stitch in the turning chain's 3rd chain.
| Item | What to get | Notes |
|---|---|---|
| Crochet thread | Size 10 is the usual start; sizes 20 and 30 go finer | The bigger the number, the thinner the thread — it's a size-down numbering, not a thickness one |
| A steel crochet hook | About 1.5–1.75 mm for size 10 — US steel size 7 (1.65 mm) is the common pairing | The hook is what sets the gauge; the swatch picks the hook |
| A tapestry needle | For weaving in the ends | Thread crochet leaves small, tidy ends |
| Rustproof pins and a blocking board | To pin the finished piece out damp | Blocking is the finish in this craft, not a garnish — see below |
| Small sharp scissors | For fastening off | Cut at the base, not the needle end |
Filet patterns publish a gauge with the thread size, and the engine starts from published numbers — two of them per size, squares across and rows down:
| Thread | Gauge the engine starts with | Where it comes from |
|---|---|---|
| Size 10 | About 4 squares and 4 rows to the inch (10 squares = 2½ in) | Kim Guzman's size 10 filet patterns |
| Size 20 | About 4½ squares across, 4.2 rows to the inch (10 squares = 2.2 × 2.4 in) | A designer's published gauges for sizes 20 and 30 |
| Size 30 | About 4¾ squares across, 4.3 rows to the inch (10 squares = 2.1 × 2.3 in) | Same published gauges |
Published gauges are starting points, not laws — yours depends on your hook and hands — so the engine's first working step for every filet piece is a swatch: crochet a 10 × 10 square of blocks (chain 33) and measure it. In size 10 thread it should come out about 2½ in across; if the swatch is bigger, drop a hook size; if it's smaller, go up. Then the app sizes the piece with your gauge instead of the printed one — 33 squares at true ¼-in gauge is 8¼ in, whatever the pattern hoped.
Thread: the engine estimates about 152 mm (6 in) of thread per block, about half that per space, plus a tenth more for the foundation chain, the turning chains and the ends. Space = half comes from the stitch counting: a space is one double crochet and two chains against a block's three double crochet. The rate itself is worked out from two published size 10 pieces — Kim Guzman's Hummingbird (3,310 yd for 37 × 45 in) and Windmill (2,400 yd for 30 × 40 in) both average about 114 mm a square at 4 to the inch, which matches a block of 152 mm when roughly half the squares are blocks. It's labelled an estimate and the engine scales it by row height for finer threads; the Supplies tab takes your own measurement, and a 10 × 10 swatch of blocks measures it in one go. Worked through: a 30 × 30 panel with about half its squares filled — 450 blocks, 450 spaces — comes out around 113 m at this rate. Ball lengths vary by brand, so check the label before trusting the last square.
Fasten off, weave the ends in with the tapestry needle, and then the step the craft leans on: blocking. Dampen the piece, pin it out square — every row straight, the grid square — and let it dry fully before unpinning. Thread crochet carries a lifetime of twist in it, and pinning is what tells that twist where to lie; the filet pattern the app sources this from says it outright: filet relies on blocking. A blocked panel that dries square with its rows straight is the difference between lace and a crumpled test swatch, and it costs one afternoon of patience. Rustproof pins, a board or a towel, done.
| Symptom | Cause | Fix |
|---|---|---|
| The picture is upside down | Chart read from the top | Read from the bottom — row 1 is the bottom row, odd rows run right to left |
| Row 1's chain count never comes out | The tutorials' "plus 1" taken as a chain | 3 per square, then 3 (block start) or 5 (space start); the "plus 1" is the row's last stitch, not a chain |
| A row ends one post short | A block worked as a space — the block-over-space junction needs 2 double crochet in the chain-2 space | Count posts against the chart: N squares, N+1 posts; rework the run |
| Open mesh looks squashed, squares pull tight | Hook too small or tension too firm for the thread | The swatch picks the hook: bigger swatch, smaller hook; smaller swatch, bigger one |
| Turning chains end in confusion | The chain-5 shortcut vs the app's chain 3 + chain 2 | They're the same stitches: chain 3 as the first post, chain 2 more to open a space |
| The piece curls and leans after the last row | Skip blocking, get drift | Pin out damp, square to the grid, every row straight; let it dry fully before unpinning |
| Not enough thread for the last rows | The published rate is an average, not a promise | Measure a 10 × 10 swatch of blocks and re-price; check the ball's label length |
Words to watch, once more, because they bite mid-pattern: US double crochet = UK treble. If a UK pattern looks three stitches short everywhere, it's the names, not you. The Glossary keeps the plain-English versions of all the app's craft words.
The drafts gallery previews all 15 filet drafts — from a Beginner Heart edging (13 squares wide: an edging, a bookmark or a band for a basket) and a 9-square-wide Bookmark, to an Intermediate HOME panel whose word you change with the Text tool, and an Advanced Medallion square, a 41-square doily with every row different. Narrow strips finish in an evening and teach the whole grid.