Crossword puzzle clue "forts made of squared timbers"

BLOCKHOUSE, a wooden or concrete fortification with ports or loopholes for defensive fire, observation, etc.

an individual thing or person; the number or figure 1

OUTPOST, a remote settlement or stronghold

PRESIDIO, (Spanish) a Spanish fort

to dress timber with a cutting tool with an arched blade set at right angles to the handle, also ADZ