  In supersymmetric models a gluino can decay into $tb\tilde{\chi}^{\pm}_1$
through a stop or a sbottom. The decay chain produces an edge structure in the
$m_{tb}$ distribution. Monte Carlo simulation studies show that the end point
and the edge height would be measured at the CERN LHC by using a sideband
subtraction technique. The stop and sbottom masses as well as their decay
branching ratios are constrained by the measurement. We study interpretations
of the measurement.
