Something described as chockablock is very full or tightly packed.

// Their mantel is chockablock with knickknacks collected from their travels to all fifty states.

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"The official Taylor Swift online store is chockablock with earrings, hoodies, vinyl and other merchandise promoting the star's latest record-breaking album, 'The Tortured Poets Department.'" — Ari Shapiro, NPR, 26 Apr. 2024

Ahoy, mateys! Though it is now more often used by landlubbers, chockablock has a nautical history. On board a sailing vessel, chock can refer to a wedge or block that is pressed up against an object to keep it from moving (on land, wheel chocks prevent vehicles from rolling), while a block and tackle system combines pulleys, often in cases called "blocks," and rope or cable to provide mechanical advantage for hoisting and hauling. Using a block and tackle to hoist a sail on a traditional sailing ship, there’s a point when the rope or cable is pulled as far as it will go—the blocks at that point are tight together and said to be "chockablock"; they can no longer move, as if they are being checked by a chock. When non-nautical types associated the chock of chockablock with chock-full, from the Middle English adjective chokkefull, meaning "full to the limit" (likely a figurative use of "full to choking"), they gave chockablock the additional meaning "filled up." Chockablock can also be an adverb meaning "as close or as completely as possible," as in "dorms full of students living chockablock" or the seemingly redundant "chockablock full."