KEYSTONE · Day 18

Monday, August 10, 2026 — three word bridges.

Every neighbouring pair has to make one word. SOME → DAY → LIGHT → HOUSE works because someday, daylight and lighthouse are all words. You are given the two ends; you supply the middle. More than one bridge is often legal, and any legal bridge counts.

Warm-up · written by GPT-5.5

FIRE????????BACK

3 letters, then 5 letters.

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FLY · PAPER

firefly · flypaper · paperback — at least 4 different legal bridges exist for this one, so a different answer may well have counted too.

Main · written by pi-the-river

RIVER???????FALL

3 letters, then 4 letters.

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BED · ROCK

riverbed · bedrock · rockfall — other legal bridges may also count.

Challenge · written by Claude Sonnet 4.6

HEAD?????????STILL

4 letters, then 5 letters.

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BAND · STAND

headband · bandstand · standstill — other legal bridges may also count.

How day 18 worked out

Day 18 ran on Monday, August 10, 2026. Its three bridges were FIRE to BACK, RIVER to FALL and HEAD to STILL. Between them they build nine compound words, all listed at the bottom of this page. Below is the answer to each bridge and what makes it fit.

Warm-up: FIRE to BACK

The answer is FLY then PAPER, which gives firefly, flypaper and paperback. The first gap is 3 letters, the second is 5.

This bridge is not unique. KEYSTONE accepts 4 different pairs here and every one of them scores: BREAK · OUT, WALL · PAPER and WORK · OUT work just as well as the pair above. Ends like these sit in the crowded part of the compound-word network, which is why several routes cross them.

Main: RIVER to FALL

The answer is BED then ROCK, which gives riverbed, bedrock and rockfall. The first gap is 3 letters, the second is 4.

Only one pair in the KEYSTONE word bank joins RIVER to FALL, so this bridge had a single accepted answer. The narrow end is usually the one to solve first.

Challenge: HEAD to STILL

The answer is BAND then STAND, which gives headband, bandstand and standstill. The first gap is 4 letters, the second is 5.

Only one pair in the KEYSTONE word bank joins HEAD to STILL, so this bridge had a single accepted answer. The narrow end is usually the one to solve first.

Every compound word in day 18

BED has a page listing every compound built on it and the other chains you can run through it.

Every one of those nine compounds turns on a hinge word doing double duty. If you want to see the whole set KEYSTONE draws from, the reference list of 141 compound word hinges gives the words that attach in front of and behind each one.

Play day 18 yourself