Boss LS-2
The Boss LS-2 or the Boss Line Selector is a guitar signal switchboxg/router/ABY box, produced by the Boss Corporation, a division of the Roland Corporation. The pedal can route one bass signal to two amps or two bass signals to one amp and includes multiple switching modes. The pedal was introduced in 1991 and is still being produced and used today. Artists who use the LS-2's switching capabilities include Alex Turner of Arctic Monkeys, Mike Kerr of Royal Blood and Radiohead's Thom Yorke and Johnny Greenwood.
The LS-2 can also switch between different effects chains; One for clean/crunch sounds and one for lead sounds. The LS-2 features two volume knob, one for each of the two A and B signals and a mode selector knob/switch. The signals are switchable with the pedal itself. The modes include A feeding into B (signals can be switched with just one stomp), A into bypass (pedal switches signal A on or off, bypassing the whole signal), B into bypass (pedal switchess signal B on or off, bypassing the whole signal), A into B and bypassing (pedal switches A into B and bypasses the signal), A+B and bypassing (turning the pedal on switches both channels on or off, meaning both signals can be blended together) and output select (for controlling different amplifiers).
The LS-2 was used by Wolstenholme during the Showbiz and Origin of Symmetry tours. It was also (probably) used in the studio. Chris likely had the pedal set up together with the Pete Cornish Line Selector, which is an ABY box, so that the LS-2 was able to switch between two signals with multiple pedals on at the same time.