We consider an abstract
analogue of Sλ#f, the truncated square function introduced by J.-O. Strömberg,
and show that it is closely related to operators appearing in the theory of tent spaces.
We suggest an approach to basic results for these spaces which differs from that
due to R.R. Coifman, Y. Meyer and E.M. Stein. Also we discuss pointwise
estimates involving Sλ#f as well as different variants of sharp maximal
functions.