How to you know if is an "one tail" or "two tail" confidence interval?

In case of two tailed confidence interval both lower bound and upper bound are stated in the interval
In case of one tailed confidence interval
either lower bound is stated or upper bound is stated (but NOT both)

The difference is with regard to the confidence coefficient (zc or tc) to be considered
for ex. for 95% level of confidence
zc = 1.96 shall be considered for two tailed confidence interval
zc = 1.645 shall be considered for one tailed confidence interval