Mathew Anderson (21) of 138 Glasgow Road, Camelon admitted having a Stanley knife without reasonable excuse or authority in Newmarket Street, Falkirk on March 29.
Falkirk Sheriff Court heard the knife was discovered after Anderson was searched by police officers who were on foot patrol in the town centre.
They had approached Anderson out of concern due to the fact he had white residue on the corners of his mouth and was acting strangely.
When questioned Anderson said he had the blade, which is extendable by three inches, because he “got a doing the other day”.
Sheriff Derek Livingston deferred sentence until October 17 for a restriction of liberty order assessment.