See if this helps

select Class, Model, [Type]

from

(

select Class, Model,

CASE [W-20-13] WHEN 'x' THEN 'W-20-13' END as [W-20-13],

CASE [W-20-14] WHEN 'x' THEN 'W-20-14' END as [W-20-14],

CASE [W-20-15] WHEN 'x' THEN 'W-20-15'...