carpets to put on some grip but there are other reasons for it too.. its so that when u pay drums the sound will be sounding better, in a sense that the carpet will actually absorb ur drum sounds and overtones a lil so it will sound better. the thing tat actually keep the bass drum from running urs bass drum spurs that has to be pointing out wards and the bass drums MUST be lifted abt an inch off the ground to no let it slip. ALOt of ppl think the drum is to be left resting on the ground but it actually has to be susppened by the spurs in the air, spurs holding in in place.. go see at pro drum set up u will notice its all off the ground.