Here's a picture of four stair
stringers with upper stair stringers still laying on the
The black arrows are pointing to the stair stringers which are the main
supports for this type of stairway. Often stair stringers are referred
to as carriages or stair horses it all depends on what part of the
country you're from.
The stair stringer needs to be fastened correctly at both the upper and lower points so the structural load is transferred correctly. If the stair stringers are not fastened correctly this could result in a safety hazard and excesses squeaking as we walk up and down the stairs.
Stair stringers should be made from a structurally sound piece of lumber.
In this picture the stringers are number one grade 2 x 14 Douglas Fir.
When selecting stair stringers material at the lumber yard try to avoid big knots and large cracks. Big knots can weaken stringers and break under extreme loads.