solid as a rock (adjective) secure: fastened, stable
Sinonime: adjusted, anchored,
bound, buttoned down,
fast,
firm,
fixed,
fortified, immovable, iron, locked, nailed, safe and sound,
set,
solid, solid as a rock,
sound,
staunch,
steady,
strong,
sure,
tenacious,
tightAntonime: loose,
moving, unfastened, unfixed, unsecure,
unstable