1. What does "solid base" mean here? A base without holes or spaces? And in relation to the whole sentence, is the writer describing some with four legs, a solid base, or wheels separately or as one thing?

2.Why isn't it "securely" instead of "secure"? Does it mean "hold the paper and, as a result, make it secure"?

gu47)Professional artists tend to identify this as one of the most important pieces of equipment in their studio. Most versions of this come in the form of a tripod, with three legs supporting the work surface. However, there are different styles of this as well, including some with four legs, a solid base, or wheels on the bottom of the legs for easy movement. Its purpose is to hold a piece of drawing paper secure and at an appropriate angle while you work on it...