**''[BT''** '':[[xy|<X>,<Y>]], [[wh|<W>,<H>]]'' **'']''**\\
**''[BT''** '':<X1>,<Y1>,<W1>,<H1>,<X2>,<Y2>,<W2>,<H2>, ...'' **'']''**

Block Transparent

A rectangular field is made transparent 

Using this modifier you can mask out loads on open freight cars or exhaust on steam engines. It is possible to define the parameters ''<X>'', ''<Y>'', ''<W>'', ''<H>'' more than once, thereby creating multiple transparent rectangular areas.  This is a simpler method than using multiple ''[BT: ]'' commands.