  The Multigap Resistive Plate Chambers (MRPCs) are gas ionization detectors
with multiple gas sub-gaps made of resistive electrodes. The high voltage (HV)
is applied on the outer surfaces of outermost resistive plates only, while the
interior plates are left electrically floating. The presence of multiple narrow
sub--gaps with high electric field results in faster signals on the outer
electrodes, thus improving the detector's time resolution. Due to their
excellent performance and relatively low cost, the MRPC detector has found
potential application in Time-of-Flight (TOF) systems. Here we present the
design, fabrication, optimization of the operating parameters such as the HV,
the gas mixture composition, and, performance of six--gap glass MRPC detectors
of area 27cm $\times$ 27 cm, which are developed in order to find application
as trigger detectors, in TOF measurement etc. The design has been optimized
with unique spacers and blockers to ensure a proper gas flow through the narrow
sub-gaps, which are 250 $\mu$m wide. The gas mixture consisting of R134A,
Isobutane and SF$_{6}$, and the fraction of each constituting gases has been
optimized after studying the MRPC performance for a set of different
concentrations. The counting efficiency of the MRPC is about 95% at $17.9$ kV.
At the same operating voltage, the time resolution, after correcting for the
walk effect, is found to be about $219$ ps.
