Silica - Part 4 This is how you shouldn't do it, in this case put the bag un te downside, sometimes the multtieffects units have space in the downside son they can not crush the silica bag, if it's not your case put it under the expression pedal, if doesn't have one check the design until you find the correct place. In the case of the Headrush pedalboard, the unit is not completely flat downside so i put it in that small place.