An inclined grate construction or apparatus in the combustion chamber of a combustion furnace, comprising a plurality of adjacent grate tubes in the longitudinal direction of the grate, said tubes being welded together through flat bars. Below the grate is disposed a grate bar carriage, which, in use, reciprocates horizontally respective to the grate. The grate bar carriage supports at least one grate bar, which is pushed through the grate via an opening in the flat bar between two adjacent grate tubes when the grate bar carriage moves towards the grate. The grate bar carriage is also vertically displaceable.