Metal Grenade Lock Puzzle: a cast-metal take-apart brain teaser from Tea-Sip. Free the central pin — two separable metal halves secured by hidden internal catches — then reassemble it to reset the challenge. It defeats trial-and-error and rewards methodical observation instead. Recommended for ages 12 and up: puzzle enthusiasts, colleagues who like a hard mechanical problem, and teens building problem-solving skills. Doubles as a desk conversation piece between solves. $11.98.