In old installations, wire splices often were covered with thick electrician's tape. That is not only a slow way to cover a splice but also a code violation. Cover every splice with an approved wire nut.
Assemble a collection of various-size nuts so you are ready for any splice. Wire nuts are color-coded according to size. The colors and sizes may vary according to manufacturer. Read the packaging to make sure the nuts you buy fit over your splices.