The invention relates to a base (3, 4, 22) for a lamp tube (1), comprising a securing part (3, 4) for stationarily securing to a front side of the lamp tube (1), and a connection part (22) having at least one electrical contact element (26) for electrically contacting a lamp holder, which connection part (22) can be twisted against the securing part (3, 4), wherein the securing part (3, 4) and the connection part (22) are electrically connected to one another by means of at least one sliding contact (4, 28). A tubular lamp (L) having a lamp tube (1) comprises a base (3, 4, 22) on at least one open end of the lamp tube (1). A method serves to assemble a base (3, 4) on a lamp, tube (1) of the tubular lamp (L). In particular, the invention is suitable for use on retrofit LED lamps as a substitute for fluorescent lamps, in particular T-type lamps, in particular T8-type lamps.