it was a nail with a large flat head embedded in the tyre. what's odd was that the tyre wasn't flat even though i hadn't driven the car for almost 24 hours & it was by chance that i noticed it, because of the large prominent head.
the neighbourhood tyre shop was closed today, so i drove to the next one that was open. i was rather surprised that the guy didn't even removed the tyre from the rim. he just pulled out the nail, pushed in a black tarry plug & inflated the tyre to check for leaks.
this is the 1st time i've seen it done this way. previously, at the other shops, the guy would remove the tyre from the rim, pull the nail out, insert the tarry plug thru the puncture, then paint the inner surface of the tyre with some glue. even at the last puncture, the guy offered me either the "standard" repair like what i just described, or a "superior" repair. in the superior repair, the repair plug is shaped like an umbrella, in contrast to being just tubular...
the flat part being positioned flush against the inner tyre wall, thereby improving the seal. this costs RM12, in contrast to the RM5 standard repair. i read somewhere that if the guy doesn't inspect the inner wall of the tyre, he has not ascertain the true extent of damage to the tyre. in a way like a doctor who prescribes cough medicine without at least listening to the chest with a stethoscope.
based on what i saw today, like an unsatisfied patient, i'll be going back to my regular tyre shop for a 2nd opinion.