Abstract: An improved string trimmer head is described. The trimmer head comprises a housing with a spool and spring assembly enclosed within the housing. The trimmer head further comprises a lid connected to the housing and a bump knob with a base and an intermediate member. The base of the bump knob is located inside the housing. The intermediate member extends outside the housing through the lid. The lid comprises an annulus which surrounds the base. The height of the annulus is greater than a maximum compressing distance of the spool when compressed by the bump knob. A segment of the intermediate member remains outside the lid when the spool is compressed. The bump knob further comprises a finger slot with an outer edge and a recessed portion. A bottom side of the outer edge is positioned farther away from the spool than the recessed portion.